[PATCH v10 00/15] s390/vfio-ap: Add live guest migration support

[PATCH v10 00/15] s390/vfio-ap: Add live guest migration support

[Anthony Krowiak]

This patch series implements live guest migration support for KVM guests
with s390 AP (Adjunct Processor) devices passed through via the VFIO
mediated device framework.

Background
~~~~~~~~~~

The vfio-ap device driver differs from typical VFIO device drivers in that
it does not virtualize a physical device. Instead, it manages AP
configuration metadata identifying the AP adapters, domains, and controls390/vfio-ap: Add live guest migration support
domains to which a guest will be granted access. These AP resources are
configured by assigning them to a vfio-ap mediated device via its sysfs
assignment interfaces. When the fd for the VFIO device is opened by
userspace, the vfio_ap device driver sets the guest's AP configuration
from the metadata stored with the mediated device. As such, the AP devices
are not accessed directly through the vfio_ap driver, so the driver has no
internal AP device state to migrate. What it does migrate is the AP
configuration metadata of the source guest.

Implementation Approach
~~~~~~~~~~~~~~~~~~~~~~~

This series implements the VFIO migration protocol using the STOP_COPY
migration flow. The key aspects are:

1. On transition of the migration state from STOP to STOP_COPY
   - The vfio_ap device driver creates a filestream for userspace to use to
     read the guest's AP configuration from the mdev

2. During the STOP_COPY phase
   - Userspace uses the filestream created in #1 to read the source guest's
     AP configuration
   - The vfio_ap device driver copies the source guest's AP configuration
     information to userspace

3. On transition of the migration state from STOP to RESUMING
   - The vfio_ap device driver creates a filestream for userspace to use to
     write the source guest's AP configuration information so it can be
     restored to the mdev on the destination host.

4. During the RESUMING phase
   - Userspace uses the filestream created in #3 to send the source guest's
     AP configuration information to the vfio_ap device driver on the
     destination host.
   - The vfio_ap device driver first verifies the source guest's AP
     configuration is compatible with the destination host's.
   - The driver restores AP configuration to the mdev on the destination
     host which automatically hot plugs the AP resources identified
     therein.

5. Documentation
   - Add live guest migration chapter to vfio-ap.rst

Compatibility Validation
~~~~~~~~~~~~~~~~~~~~~~~~

The series includes comprehensive validation to ensure source and
destination AP configurations are compatible. For each queue, the following
characteristics must match:

- AP type (target must be same or newer than source)
- Installed facilities (APSC, APQKM, AP4KC, SLCF)
- Operating mode (CCA, Accelerator, XCP)
- APXA facility setting
- Classification (native vs stateless functions)
- Queue usability (binding/associated state)

When incompatibilities are detected, migration fails with detailed error
messages identifying the specific queue and characteristic that caused
the failure.

Configuration Management
~~~~~~~~~~~~~~~~~~~~~~~~

This implementation does not prevent configuration changes during
migration. Configuration stability is an orchestration-layer
responsibility, consistent with other VFIO device types. The driver's
role is to validate configurations and provide clear diagnostics when
incompatibilities are detected, enabling orchestration tools to implement
appropriate policies.

QEMU patches exploiting this series:
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
https://lore.kernel.org/qemu-devel/20260409141352.997844-1-akrowiak@linux.ibm.com/

Change log v9 => v10:
~~~~~~~~~~~~~~~~~~~~
Patch 03/15: Functions to initialize/release vfio device migration data
* vfio_ap_mdev_init_dev()
  ~ Drop unnecessary matrix_dev->mdevs_lock around migration init/release calls
* Deferred setting vdev.mig_ops and migration_flags to patch 13/15 so migration
  is not advertised while callbacks are stubs
* Fixed kernel-doc parameter tag mismatch in comments

Patch 04/15: Reset migration state in VFIO_DEVICE_RESET ioctl handler
* Updated commit message to clarify that resetting migration state releases
  open migration file buffers while retaining mig_data

Patch 05/15: Callback to get/set vfio device mig state during guest migration
* vfio_ap_set_state()
  ~ Removed dead/unreachable branches

Patch 06/15: Transition guest migration state from STOP to STOP_COPY
* vfio_ap_stop_copy_read()
  ~ Added parameter names to function prototype to fix GCC < 11 build errors

Patch 07/15: File ops called to save the vfio device migration state
* get_hardware_info_for_queue()
  ~ Use ap_test_queue() with the T-bit set instead of ap_tapq()
  ~ Accept all 5 architecture-defined response codes returning valid hwinfo
    (NORMAL, RESET_IN_PROGRESS, DECONFIGURED, CHECKSTOPPED, BUSY); unknown RCs
    return -EIO
  ~ Removed retry loop and msleep(), eliminating sleep-under-lock
* vfio_ap_stop_copy_read()
  ~ Copy data into a bounce buffer under mdevs_lock and invoke copy_to_user()
    outside the lock to avoid holding the lock across user memory faults
  ~ Changed *pos check to if (*pos < 0) return -EINVAL
* vfio_ap_config_size()
  ~ Changed parameter type from int * to unsigned int * and dropped (int *) cast
* Incompatibility reporting
  ~ Report APQN in error log when AP type mismatch is detected
  ~ Corrected QINFO_DATA_MASK bit range documentation comments
* Dropped unnecessary compat_ioctl file operation

Patch 08/15: Transition device migration state from STOP to RESUMING
* Updated commit message describing state transitions
r
Patch 09/15: Prepare lock helpers and matrix init for cross-file use
* Updated commit message to clarify that assert_has_update_locks_for_mdev()
  is a newly introduced helper

Patch 10/15: File ops called to resume the vfio device migration
* Switched to pre-configured destination mdev model:
  ~ Destination mdev must be pre-configured by admin with crypto resources
  ~ Migration stream contents are strictly validated against destination
    matrix_mdev configuration and shadow_apcb; stream data no longer mutates
    matrix or shadow_apcb
  ~ Removed setup_ap_matrix_from_ap_config() and dynamic guest re-configuration
* do_post_copy_validation()
  ~ Validate stream magic, version, and header consistency
  ~ Verify that incoming APQNs and cdoms are a subset of destination shadow_apcb
  ~ Enforce that all passed-through queues match the pre-configured matrix
* vfio_ap_resuming_write()
  ~ Changed *pos check to if (*pos < 0) return -EINVAL
* Fixed stray colon in kernel log message

Patch 11/15: Transition device migration state to from/to STOP
* vfio_ap_set_state()
  ~ Reject transition from RESUMING to STOP with -EINVAL if the full
    migration configuration data stream has not been received

Patch 12/15: Callback to get the size of data to be migrated during guest migration
* Replaced size calculation logic with direct call to vfio_ap_config_size()

Patch 13/15: Set up for vfio-ap device migration
* Set vdev.mig_ops and VFIO_MIGRATION_STOP_COPY flag in vfio_ap_mdev_probe()
  once all migration callbacks are fully implemented
* Cleaned up probe function comments regarding lock ordering

Patch 14/15: Add 'migration' feature to sysfs 'features' attribute
* Renamed sysfs feature attribute from 'migratable' to 'migration'

Patch 15/15: Add live guest migration chapter to vfio-ap.rst
* Corrected erroneous sentence swapping source host with destination host
* Updated documentation for pre-configured destination mdev requirement
* Fixed error code and console output in incompatible-queue example
  (ret: -22 / -EINVAL)
* Synchronized kernel and console log messages and format specifiers with
  the exact strings in drivers/s390/crypto/vfio_ap_migration.c

Anthony Krowiak (15):
  s390/vfio-ap: Provide function to get the number of queues assigned to
    mdev
  s390/vfio-ap: Data structures for facilitating vfio device migration
  s390/vfio-ap: Functions to initialize/release vfio device migration
    data
  s390/vfio-ap: Reset migration state in VFIO_DEVICE_RESET ioctl handler
  s390/vfio-ap: Callback to get/set vfio device mig state during guest
    migration
  s390/vfio-ap: Transition guest migration state from STOP to STOP_COPY
  s390/vfio-ap: File ops called to save the vfio device migration state
  s390/vfio-ap: Transition device migration state from STOP to RESUMING
  s390/vfio-ap: Prepare lock helpers and matrix init for cross-file use
  s390/vfio-ap: File ops called to resume the vfio device migration
  s390/vfio-ap: Transition device migration state to from/to STOP
  s390/vfio-ap: Callback to get the size of data to be migrated during
    guest migration
  s390/vfio-ap: Set up for vfio-ap device migration
  s390/vfio-ap: Add 'migration' feature to sysfs 'features' attribute
  s390/vfio-ap: Add live guest migration chapter to vfio-ap.rst

 Documentation/arch/s390/vfio-ap.rst     |  641 ++++++++--
 drivers/s390/crypto/Makefile            |    2 +-
 drivers/s390/crypto/vfio_ap_drv.c       |   14 +-
 drivers/s390/crypto/vfio_ap_migration.c | 1419 +++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       |  120 +-
 drivers/s390/crypto/vfio_ap_private.h   |   70 ++
 6 files changed, 2111 insertions(+), 155 deletions(-)
 create mode 100644 drivers/s390/crypto/vfio_ap_migration.c

-- 
2.53.0

[PATCH v10 01/15] s390/vfio-ap: Provide function to get the number of queues assigned to mdev

[Anthony Krowiak]

Provides a function that returns the number of queues that are or will be
passed through to a guest when the mdev is attached to a guest.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 8 ++++++++
 drivers/s390/crypto/vfio_ap_private.h | 2 ++
 2 files changed, 10 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 4db878c18f41..345c52a328ad 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -2105,6 +2105,14 @@ static void vfio_ap_mdev_request(struct vfio_device *vdev, unsigned int count)
 	release_update_locks_for_mdev(matrix_mdev);
 }
 
+unsigned int vfio_ap_mdev_get_num_queues(struct ap_matrix *ap_matrix)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	return bitmap_weight(ap_matrix->apm, AP_DEVICES) *
+	       bitmap_weight(ap_matrix->aqm, AP_DOMAINS);
+}
+
 static int vfio_ap_mdev_get_device_info(unsigned long arg)
 {
 	unsigned long minsz;
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 9bff666b0b35..12d7d240addd 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -152,6 +152,8 @@ struct vfio_ap_queue {
 	struct work_struct reset_work;
 };
 
+unsigned int vfio_ap_mdev_get_num_queues(struct ap_matrix *ap_matrix);
+
 int vfio_ap_mdev_register(void);
 void vfio_ap_mdev_unregister(void);
 
-- 
2.53.0

[PATCH v10 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration

[Anthony Krowiak]

Creates the data structures used to facilitate state transitions during
vfio device migration.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
---
 drivers/s390/crypto/Makefile            |   2 +-
 drivers/s390/crypto/vfio_ap_migration.c | 121 ++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_private.h   |   5 +
 3 files changed, 127 insertions(+), 1 deletion(-)
 create mode 100644 drivers/s390/crypto/vfio_ap_migration.c

diff --git a/drivers/s390/crypto/Makefile b/drivers/s390/crypto/Makefile
index e83c6603c858..20f29184825a 100644
--- a/drivers/s390/crypto/Makefile
+++ b/drivers/s390/crypto/Makefile
@@ -34,5 +34,5 @@ pkey-uv-objs := pkey_uv.o
 obj-$(CONFIG_PKEY_UV) += pkey-uv.o
 
 # adjunct processor matrix
-vfio_ap-objs := vfio_ap_drv.o vfio_ap_ops.o
+vfio_ap-objs := vfio_ap_drv.o vfio_ap_ops.o vfio_ap_migration.o
 obj-$(CONFIG_VFIO_AP) += vfio_ap.o
diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
new file mode 100644
index 000000000000..f01a37e4c418
--- /dev/null
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -0,0 +1,121 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Drives vfio_ap mdev migration.
+ *
+ * Copyright IBM Corp. 2025
+ */
+#include "vfio_ap_private.h"
+
+/* Magic number and version for the vfio_ap_config migration blob */
+#define VFIO_AP_MIG_MAGIC			0x76666170U  /* "vfap" */
+#define VFIO_AP_MIG_VERSION			1U
+
+/**
+ * struct vfio_ap_migration_file
+ *
+ * This object is used for chunk processing of multiple reads and writes of
+ * AP configuration information.
+ *
+ * @filp:	file stream used to read or write AP configuration data
+ * @ap_config:	object used to store AP configuration data between read or write
+ *		calls
+ * @config_sz:	the size (in bytes) of @ap_config
+ */
+struct vfio_ap_migration_file {
+	struct file		*filp;
+	struct vfio_ap_config	*ap_config;
+	unsigned long		config_sz;
+};
+
+/**
+ * struct vfio_ap_migration_data:
+ *
+ * Manages the migration state for the VFIO device that maintains the AP
+ * configuration of the guest being migrated.
+ *
+ * @mig_state:			the current migration state
+ * @resuming_mig_data_complete:	indicates whether a complete, valid AP
+ *				configuration blob was received (true) or not (false)
+ *				during the RESUMING phase. This must be checked
+ *				on RESUMING->STOP to enforce the vfio.h
+ *				requirement that SET_STATE must fail if the data
+ *				is incomplete or invalid.
+ * @resuming_mig_file:		the object used to restore the state of the
+ *				vfio-ap device on the destination host.
+ * @stop_copy_mig_file:		the object used to store the AP configuration of
+ *				the source guest for transfer to the destination
+ *				host.
+ */
+struct vfio_ap_migration_data {
+	enum vfio_device_mig_state	mig_state;
+	bool				resuming_mig_data_complete;
+	struct vfio_ap_migration_file	resuming_mig_file;
+	struct vfio_ap_migration_file	stop_copy_mig_file;
+};
+
+/**
+ * struct vfio_ap_queue_info - the information for an AP queue
+ *
+ * @data: contains the queue information returned in GR2 from the PQAP(TAPQ)
+ *	  command
+ * @apqn: the APQN of the queue
+ * @reserved: padding to ensure consistent structure size across platforms
+ */
+struct vfio_ap_queue_info {
+	u64 data;
+	u16 apqn;
+	u8  reserved[6];
+};
+
+/**
+ * struct vfio_ap_config:
+ *
+ * Stores the state of a guest's AP configuration.
+ *
+ * VFIO device migration state transition from STOP to STOP_COPY:
+ * -------------------------------------------------------------
+ * When the migration state transitions from STOP to STOP_COPY, the vfio_ap device
+ * driver will open a file stream in read-only mode and return the fd to userspace.
+ * This fd is used during the STOP_COPY phase to read the current state of the
+ * vfio-ap device on the source host. In response, the driver will store the
+ * source guest's AP configuration data in a vfio_ap_config object and copy it to
+ * userspace.
+ *
+ * VFIO device migration state transition from STOP to RESUMING:
+ * ------------------------------------------------------------
+ * When the VFIO migration state transitions from STOP to RESUMING,
+ * the vfio_ap device driver will open a file stream in write-only mode and
+ * return the fd to userspace. This fd is used during the RESUMING phase to
+ * write the source guest's vfio_ap_config data that was read in during the
+ * STOP_COPY phase to the vfio_ap device driver on the destination host. In
+ * response, the device driver will copy the data sent from userspace to a
+ * vfio_ap_config instance which is then used to update the destination guest's
+ * AP configuration.
+ *
+ * Since the source and destination hosts may be running different versions of
+ * the linux kernel, the vfio_ap_config object provides two fields (@magic and
+ * @version) which must be set by the source device driver and verified by the
+ * destination device driver to ensure the migration ABI of the source and
+ * destination hosts are compatible.
+ *
+ * Note: Since a guest's AP configuration could be comprised of a large number of
+ *	 AP queue devices, a vfio_ap_config object should be allocated using
+ *	 kvzalloc.
+ *
+ * @magic:	identifies this as a valid vfio_ap_config migration blob;
+ *		must equal VFIO_AP_MIG_MAGIC
+ * @version:	layout version; must equal VFIO_AP_MIG_VERSION
+ * @num_queues:	the number of queues passed through to the guest
+ * @reserved:	padding to ensure proper alignment of @adm
+ * @adm:	bitmap specifying the control domains in the AP configuration
+ * @qinfo:	an array of vfio_ap_queue_info objects, each specifying the
+ *		queue information for a queue passed through to the guest
+ */
+struct vfio_ap_config {
+	u32				magic;
+	u32				version;
+	u32				num_queues;
+	u8				reserved[4];
+	u64				adm[DIV_ROUND_UP(AP_DOMAINS, 64)];
+	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
+};
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 12d7d240addd..172471793e22 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -91,6 +91,9 @@ struct ap_queue_table {
 	DECLARE_HASHTABLE(queues, 8);
 };
 
+/* Forward declaration for migration data structure */
+struct vfio_ap_migration_data;
+
 /**
  * struct ap_matrix_mdev - Contains the data associated with a matrix mediated
  *			   device.
@@ -110,6 +113,7 @@ struct ap_queue_table {
  * @aqm_add:	bitmap of APQIs added to the host's AP configuration
  * @adm_add:	bitmap of control domain numbers added to the host's AP
  *		configuration
+ * @mig_data:  vfio device migration data
  */
 struct ap_matrix_mdev {
 	struct vfio_device vdev;
@@ -125,6 +129,7 @@ struct ap_matrix_mdev {
 	DECLARE_BITMAP(apm_add, AP_DEVICES);
 	DECLARE_BITMAP(aqm_add, AP_DOMAINS);
 	DECLARE_BITMAP(adm_add, AP_DOMAINS);
+	struct vfio_ap_migration_data *mig_data;
 };
 
 /**
-- 
2.53.0

[PATCH v10 03/15] s390/vfio-ap: Functions to initialize/release vfio device migration data

[Anthony Krowiak]

Provides the functions that initialize and release the data structures
used during live guest migration:

* vfio_ap_init_migration_data

  Allocates and initializes the object used to maintain the state of the
  VFIO migration. It is called when the VFIO device is opened.

* vfio_ap_release_migration_data

  Frees the memory of the object used to maintain the VFIO migration
  state. It is called when the VFIO device release callback is invoked
  and when the VFIO device is closed.

* vfio_ap_release_mig_files

  This function is called from the vfio_ap_release_migration_data
  function (above) and releases the vfio_ap_migration_file objects
  contained within the vfio_ap_migation_data object used to maintain
  the state of the VFIO migration process.

* vfio_ap_release_stop_copy_file

  This function is called from the vfio_ap_release_mig_files function
  (above) to release the vfio_ap_migration_file used during the
  STOP_COPY phase of migration. For now, this is a stub function that
  will be fully implemented in a subsequent patch after the
  vfio_ap_config object referenced within is allocated, as it will
  need to be freed according to how it is allocated.

* vfio_ap_release_resuming_file

  This function is called from the vfio_ap_release_mig_files function
  (above) to release the vfio_ap_migration_file used during the
  RESUMING phase of migration. For now, this is a stub function that
  will be fully implemented in a subsequent patch after the
  vfio_ap_config object referenced within is allocated, as it will
  need to be freed according to how it is allocated.

* vfio_ap_set_state, vfio_ap_get_state and vfio_ap_get_data_size

  These three functions are callback functions assigned to the
  vfio_ap_migration_ops (.migration_set_state, .migration_get_state
  and .migration_get_data_size function pointers).

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 97 +++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       | 41 +++++++++--
 drivers/s390/crypto/vfio_ap_private.h   |  3 +
 3 files changed, 136 insertions(+), 5 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index f01a37e4c418..ba86a1afbb33 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -4,6 +4,7 @@
  *
  * Copyright IBM Corp. 2025
  */
+#include <linux/file.h>
 #include "vfio_ap_private.h"
 
 /* Magic number and version for the vfio_ap_config migration blob */
@@ -119,3 +120,99 @@ struct vfio_ap_config {
 	u64				adm[DIV_ROUND_UP(AP_DOMAINS, 64)];
 	struct vfio_ap_queue_info	qinfo[] __counted_by(num_queues);
 };
+
+static void
+vfio_ap_release_stop_copy_file(struct vfio_ap_migration_data *mig_data)
+{
+	kvfree(mig_data->stop_copy_mig_file.ap_config);
+	mig_data->stop_copy_mig_file.ap_config = NULL;
+	mig_data->stop_copy_mig_file.config_sz = 0;
+	mig_data->stop_copy_mig_file.filp = NULL;
+}
+
+static void vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_data)
+{
+	kvfree(mig_data->resuming_mig_file.ap_config);
+	mig_data->resuming_mig_file.ap_config = NULL;
+	mig_data->resuming_mig_file.config_sz = 0;
+	mig_data->resuming_mig_file.filp = NULL;
+	mig_data->resuming_mig_data_complete = false;
+}
+
+/**
+ * vfio_ap_init_migration_data - initialize migration data and functions
+ *
+ * @matrix_mdev: pointer to object containing the mdev state
+ *
+ * Return: zero if initialization is successful; otherwise, returns a error.
+ */
+int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev)
+{
+	struct vfio_ap_migration_data *mig_data;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	/*
+	 * Live guest migration is not supported for SE guests, so there is no
+	 * need to initialize the migration data.
+	 */
+	if (ap_is_se_guest())
+		return 0;
+
+	mig_data = kzalloc_obj(struct vfio_ap_migration_data, GFP_KERNEL);
+	if (!mig_data)
+		return -ENOMEM;
+
+	mig_data->mig_state = VFIO_DEVICE_STATE_RUNNING;
+	mig_data->resuming_mig_data_complete = false;
+	matrix_mdev->mig_data = mig_data;
+
+	return 0;
+}
+
+/**
+ * vfio_ap_release_mig_files:
+ *
+ * Free the ap_config buffers for any open migration FDs. Although a
+ * migration FD may still be held open by userspace, it is safe to free
+ * mig_data here because:
+ *
+ *   1. matrix_mdev remains valid for the lifetime of any open migration
+ *      FD via the vfio_device registration reference taken in
+ *      vfio_ap_open_file_stream() and dropped in
+ *      vfio_ap_release_mig_file().
+ *
+ *   2. mig_data is only accessed by the migration file ops
+ *      (vfio_ap_stop_copy_read, vfio_ap_resuming_write) under
+ *      mdevs_lock. Once mig_data is set to NULL by the caller, those
+ *      paths will see NULL and return -ENODEV before dereferencing it.
+ *
+ * @matrix_mdev: The object used to maintain the state for a mediated device
+ */
+static void vfio_ap_release_mig_files(struct ap_matrix_mdev *matrix_mdev)
+{
+	struct vfio_ap_migration_data *mig_data;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	mig_data = matrix_mdev->mig_data;
+	vfio_ap_release_stop_copy_file(mig_data);
+	vfio_ap_release_resuming_file(mig_data);
+}
+
+/**
+ * vfio_ap_release_migration_data: reclaim private migration data
+ *
+ * @mdev: pointer to the object containing the state of the mdev
+ */
+void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!matrix_mdev->mig_data)
+		return;
+
+	vfio_ap_release_mig_files(matrix_mdev);
+	kfree(matrix_mdev->mig_data);
+	matrix_mdev->mig_data = NULL;
+}
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 345c52a328ad..9cbc5ecb19d5 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -794,6 +794,16 @@ static int vfio_ap_mdev_init_dev(struct vfio_device *vdev)
 	return 0;
 }
 
+static void vfio_ap_mdev_release_dev(struct vfio_device *vdev)
+{
+	struct ap_matrix_mdev *matrix_mdev;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	vfio_ap_release_migration_data(matrix_mdev);
+	mutex_unlock(&matrix_dev->mdevs_lock);
+}
+
 static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 {
 	struct ap_matrix_mdev *matrix_mdev;
@@ -2059,19 +2069,39 @@ static int vfio_ap_mdev_reset_qlist(struct list_head *qlist)
 
 static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
 {
-	struct ap_matrix_mdev *matrix_mdev =
-		container_of(vdev, struct ap_matrix_mdev, vdev);
+	struct ap_matrix_mdev *matrix_mdev;
+	int ret;
 
 	if (!vdev->kvm)
 		return -EINVAL;
 
-	return vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	ret = vfio_ap_init_migration_data(matrix_mdev);
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	if (ret)
+		return ret;
+
+	ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
+	if (ret) {
+		/* Clean up migration data on failure */
+		mutex_lock(&matrix_dev->mdevs_lock);
+		vfio_ap_release_migration_data(matrix_mdev);
+		mutex_unlock(&matrix_dev->mdevs_lock);
+	}
+
+	return ret;
 }
 
 static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
 {
-	struct ap_matrix_mdev *matrix_mdev =
-		container_of(vdev, struct ap_matrix_mdev, vdev);
+	struct ap_matrix_mdev *matrix_mdev;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	vfio_ap_release_migration_data(matrix_mdev);
+	mutex_unlock(&matrix_dev->mdevs_lock);
 
 	vfio_ap_mdev_unset_kvm(matrix_mdev);
 }
@@ -2397,6 +2427,7 @@ static const struct attribute_group vfio_queue_attr_group = {
 
 static const struct vfio_device_ops vfio_ap_matrix_dev_ops = {
 	.init = vfio_ap_mdev_init_dev,
+	.release = vfio_ap_mdev_release_dev,
 	.open_device = vfio_ap_mdev_open_device,
 	.close_device = vfio_ap_mdev_close_device,
 	.ioctl = vfio_ap_mdev_ioctl,
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 172471793e22..aa8a22585204 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -172,4 +172,7 @@ void vfio_ap_on_cfg_changed(struct ap_config_info *new_config_info,
 void vfio_ap_on_scan_complete(struct ap_config_info *new_config_info,
 			      struct ap_config_info *old_config_info);
 
+int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
+void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
+
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.53.0

[PATCH v10 04/15] s390/vfio-ap: Reset migration state in VFIO_DEVICE_RESET ioctl handler

[Anthony Krowiak]

According to the VFIO migration specifications, userspace must issue a
VFIO_DEVICE_RESET ioctl if a vfio device enters an error state or fails a
state transition to recover the device and return its migration state to
RUNNING. This patch adds a function that is called when a VFIO_DEVICE_RESET
is issued that releases any open migration file buffers and resets the
migration state to RUNNING.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 20 ++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       | 11 +++++++++++
 drivers/s390/crypto/vfio_ap_private.h   |  1 +
 3 files changed, 32 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index ba86a1afbb33..5d898be0d058 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -216,3 +216,23 @@ void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev)
 	kfree(matrix_mdev->mig_data);
 	matrix_mdev->mig_data = NULL;
 }
+
+/**
+ * vfio_ap_reset_migration_state - Reset the vfio-ap migration state
+ *
+ * @matrix_mdev: pointer to the object maintaining the vfio-ap device state
+ *
+ * Called during VFIO_DEVICE_RESET to clean up any active migration
+ * state and reset the device to RUNNING state as required by the VFIO
+ * migration specification.
+ */
+void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!matrix_mdev->mig_data)
+		return;
+
+	vfio_ap_release_mig_files(matrix_mdev);
+	matrix_mdev->mig_data->mig_state = VFIO_DEVICE_STATE_RUNNING;
+}
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 9cbc5ecb19d5..635c8a20af86 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -2320,6 +2320,17 @@ static ssize_t vfio_ap_mdev_ioctl(struct vfio_device *vdev,
 		break;
 	case VFIO_DEVICE_RESET:
 		ret = vfio_ap_mdev_reset_queues(matrix_mdev);
+		/*
+		 * Reset the migration state unconditionally, regardless of
+		 * whether the hardware queue reset succeeded. The migration
+		 * state tracks the AP configuration transfer lifecycle and is
+		 * independent of the hardware queue reset outcome. The VFIO
+		 * migration spec designates VFIO_DEVICE_RESET as the mechanism
+		 * to return device_state to RUNNING (e.g. to recover from
+		 * ERROR), so the migration state must be cleaned up even when
+		 * one or more queues fail to reset.
+		 */
+		vfio_ap_reset_migration_state(matrix_mdev);
 		break;
 	case VFIO_DEVICE_GET_IRQ_INFO:
 		ret = vfio_ap_get_irq_info(arg);
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index aa8a22585204..c6e577064e7e 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -174,5 +174,6 @@ void vfio_ap_on_scan_complete(struct ap_config_info *new_config_info,
 
 int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
+void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev);
 
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.53.0

[PATCH v10 05/15] s390/vfio-ap: Callback to get/set vfio device mig state during guest migration

[Anthony Krowiak]

Implements two callbacks related to the current state of a vfio-ap device:
* The callback that sets a new migration state of a vfio-ap device during
  live migration of guests with pass-through access to AP devices. This
  callback is mandatory for VFIO_DEVICE_FEATURE_MIGRATION support.

  The function pointer for this callback is specified via the
  'migration_set_state' field of the 'vfio_migration_ops' structure
  which is stored with the VFIO device when the 'vfio_device'
  structure representing the mediated device is initialized.

* The callback that returns the current vfio device migration state during
  live migration of guests with pass-through access to AP devices.

  The function pointer for this callback is specified via the
  'migration_get_state' field of the 'vfio_migration_ops' structure
  which is stored with the VFIO device when the 'vfio_device'
  structure representing the mediated device is initialized.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 144 ++++++++++++++++++++++++
 1 file changed, 144 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 5d898be0d058..07a4b5c1d6dd 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -139,6 +139,150 @@ static void vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_dat
 	mig_data->resuming_mig_data_complete = false;
 }
 
+static struct file *
+vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
+			    enum vfio_device_mig_state new_state)
+{
+	struct vfio_ap_migration_data *mig_data;
+	enum vfio_device_mig_state cur_state;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+	mig_data = matrix_mdev->mig_data;
+	cur_state = mig_data->mig_state;
+	dev_dbg(matrix_mdev->vdev.dev, "%s: %d -> %d\n", __func__, cur_state,
+		new_state);
+
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_STOP_COPY) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_RESUMING) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
+	     new_state == VFIO_DEVICE_STATE_STOP) ||
+	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
+	     new_state == VFIO_DEVICE_STATE_STOP)) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
+	     new_state == VFIO_DEVICE_STATE_RUNNING) ||
+	    (cur_state == VFIO_DEVICE_STATE_RUNNING &&
+	     new_state == VFIO_DEVICE_STATE_STOP)) {
+		/* TODO */
+		return ERR_PTR(-EOPNOTSUPP);
+	}
+
+	/* vfio_mig_get_next_state() does not use arcs other than the above */
+	WARN_ON(true);
+
+	return ERR_PTR(-EINVAL);
+}
+
+static struct file *vfio_ap_set_state(struct vfio_device *vdev,
+				      enum vfio_device_mig_state  new_state)
+{
+	int ret;
+	struct file *filp = NULL;
+	struct ap_matrix_mdev *matrix_mdev;
+	enum vfio_device_mig_state next_state;
+	struct vfio_ap_migration_data *mig_data;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	mig_data = matrix_mdev->mig_data;
+
+	/*
+	 * The mig_data pointer is set in the vfio_ap_init_migration_data
+	 * function which is called when the vfio-ap device fd is opened.
+	 * Since the implicit pre-open state is RUNNING, a request to set
+	 * RUNNING is a no-op. Any other state transition is invalid before
+	 * open_device.
+	 */
+	if (!mig_data) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		if (new_state == VFIO_DEVICE_STATE_RUNNING)
+			return NULL;
+		return ERR_PTR(-ENODEV);
+	}
+
+	dev_dbg(vdev->dev, "%s -> %d\n", __func__, new_state);
+
+	while (mig_data->mig_state != new_state) {
+		ret = vfio_mig_get_next_state(vdev, mig_data->mig_state,
+					      new_state, &next_state);
+		if (ret) {
+			filp = ERR_PTR(ret);
+			break;
+		}
+
+		filp = vfio_ap_transition_to_state(matrix_mdev, next_state);
+		if (IS_ERR(filp))
+			break;
+
+		mig_data->mig_state = next_state;
+
+		if (WARN_ON(filp && new_state != next_state)) {
+			fput(filp);
+			filp = ERR_PTR(-EINVAL);
+			break;
+		}
+	}
+
+	if (mig_data->mig_state == VFIO_DEVICE_STATE_ERROR)
+		filp = ERR_PTR(-EIO);
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return filp;
+}
+
+static int vfio_ap_get_state(struct vfio_device *vdev,
+			     enum vfio_device_mig_state  *current_state)
+{
+	struct ap_matrix_mdev *matrix_mdev;
+	struct vfio_ap_migration_data *mig_data;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	mig_data =  matrix_mdev->mig_data;
+
+	/*
+	 * The mig_data pointer is set in the vfio_ap_init_migration_data
+	 * function which is called when the vfio-ap device fd is opened.
+	 * If mig_data is NULL, report RUNNING as the implicit pre-open state
+	 * so userspace doesn't need to perform any state transition before the
+	 * device becomes active.
+	 */
+	*current_state = (mig_data) ? mig_data->mig_state :
+				      VFIO_DEVICE_STATE_RUNNING;
+
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return 0;
+}
+
+static int vfio_ap_get_data_size(struct vfio_device *vdev,
+				 unsigned long *stop_copy_length)
+{
+	return -EOPNOTSUPP;
+}
+
+static const struct vfio_migration_ops vfio_ap_migration_ops = {
+	.migration_set_state = vfio_ap_set_state,
+	.migration_get_state = vfio_ap_get_state,
+	.migration_get_data_size = vfio_ap_get_data_size,
+};
+
 /**
  * vfio_ap_init_migration_data - initialize migration data and functions
  *
-- 
2.53.0

[PATCH v10 06/15] s390/vfio-ap: Transition guest migration state from STOP to STOP_COPY

[Anthony Krowiak]

The transition of the guest migration state from VFIO_DEVICE_STATE_STOP to
VFIO_DEVICE_STATE_STOP_COPY begins the process of saving the
vfio device state. The vfio device state is comprised of the guest's
AP configuration which specifies the adapters, domains and control
domains to which the guest will be given access.

To begin the process of saving the vfio device state, the VFIO AP device
driver opens a file stream that will be used to read the source guest's
AP configuration.

Note:
This commit introduces the file operations structure for migration state
files with a stub implementation of the read operation. The complete
implementation is provided in the subsequent commit.

This incremental approach allows for easier review of the migration
infrastructure setup separate from the actual implementation logic.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 72 ++++++++++++++++++++++++-
 1 file changed, 70 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 07a4b5c1d6dd..bc216c51a1a7 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -4,6 +4,7 @@
  *
  * Copyright IBM Corp. 2025
  */
+#include <linux/anon_inodes.h>
 #include <linux/file.h>
 #include "vfio_ap_private.h"
 
@@ -139,6 +140,61 @@ static void vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_dat
 	mig_data->resuming_mig_data_complete = false;
 }
 
+static ssize_t
+vfio_ap_stop_copy_read(struct file *filp, char __user *buf, size_t len,
+		       loff_t *pos)
+{
+	/* TODO */
+	return -EOPNOTSUPP;
+}
+
+static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
+{
+	struct ap_matrix_mdev *matrix_mdev = filp->private_data;
+
+	/*
+	 * The VFIO device lifetime is tied to migration FD lifetime (see
+	 * vfio_ap_open_file_stream() function) to guarantee that the
+	 * matrix_mdev remains valid for every read/write operation. Let's drop
+	 * it here since the migration FD is being released.
+	 */
+	vfio_device_put_registration(&matrix_mdev->vdev);
+	return 0;
+}
+
+static const struct file_operations vfio_ap_stop_copy_fops = {
+	.owner = THIS_MODULE,
+	.read = vfio_ap_stop_copy_read,
+	.release = vfio_ap_release_mig_file,
+};
+
+static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
+					     const struct file_operations *fops,
+					     int flags)
+{
+	struct file *filp;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	/*
+	 * Pin the vfio_device registration so that matrix_mdev cannot be freed
+	 * while the migration FD is still open. The matching put is in
+	 * vfio_ap_release_mig_file().
+	 */
+	if (!vfio_device_try_get_registration(&matrix_mdev->vdev))
+		return ERR_PTR(-ENODEV);
+
+	filp = anon_inode_getfile("vfio_ap_mig_file", fops, matrix_mdev, flags);
+	if (IS_ERR(filp)) {
+		vfio_device_put_registration(&matrix_mdev->vdev);
+		return filp;
+	}
+
+	stream_open(filp->f_inode, filp);
+
+	return filp;
+}
+
 static struct file *
 vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 			    enum vfio_device_mig_state new_state)
@@ -152,10 +208,22 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 	dev_dbg(matrix_mdev->vdev.dev, "%s: %d -> %d\n", __func__, cur_state,
 		new_state);
 
+	/*
+	 * Begins the process of saving the vfio device state by creating and
+	 * returning a streaming data_fd to be used to read out the internal
+	 * state of the vfio-ap device on the source host.
+	 */
 	if (cur_state == VFIO_DEVICE_STATE_STOP &&
 	    new_state == VFIO_DEVICE_STATE_STOP_COPY) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+		struct file *filp = vfio_ap_open_file_stream(matrix_mdev,
+							     &vfio_ap_stop_copy_fops,
+							     O_RDONLY);
+		if (IS_ERR(filp))
+			return ERR_CAST(filp);
+
+		mig_data->stop_copy_mig_file.filp = filp;
+
+		return filp;
 	}
 
 	if (cur_state == VFIO_DEVICE_STATE_STOP &&
-- 
2.53.0

[PATCH v10 07/15] s390/vfio-ap: File ops called to save the vfio device migration state

[Anthony Krowiak]

Implements the read callback function that was added to the
file_operations structure for the file created to save the state of the
vfio-ap device when the migration state transitioned from STOP to
to the STOP_COPY state.

This function copies the guest's AP configuration information to
userspace. The information copied is comprised of the APQN of each queue
device passed through to the guest along with its hardware information.
This state data will be transferred to the vfio_ap device driver on the
destination host when the state is transitioned to RESUMING.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 272 +++++++++++++++++++++++-
 1 file changed, 264 insertions(+), 8 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index bc216c51a1a7..f9b00fb89410 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -6,6 +6,7 @@
  */
 #include <linux/anon_inodes.h>
 #include <linux/file.h>
+#include <linux/slab.h>
 #include "vfio_ap_private.h"
 
 /* Magic number and version for the vfio_ap_config migration blob */
@@ -140,14 +141,6 @@ static void vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_dat
 	mig_data->resuming_mig_data_complete = false;
 }
 
-static ssize_t
-vfio_ap_stop_copy_read(struct file *filp, char __user *buf, size_t len,
-		       loff_t *pos)
-{
-	/* TODO */
-	return -EOPNOTSUPP;
-}
-
 static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 {
 	struct ap_matrix_mdev *matrix_mdev = filp->private_data;
@@ -162,6 +155,269 @@ static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 	return 0;
 }
 
+/**
+ * validate_stop_copy_read_parms: Validate the input parameters to the
+ *                                vfio_ap_stop_copy_read function
+ *
+ * @filp: Pointer to the file stream used to read the vfio-ap device state
+ * @len:  The length of the data to be read
+ *
+ * Verify the following:
+ * - @filp private data is an ap_matrix_mdev instance
+ * - @filp is the instance opened when state transitioned from STOP to STOP_COPY
+ * - @filp->f_pos + @len does not cause integer overflow
+ *
+ * Returns: 0 if the parameters pass validation; otherwise returns an error
+ */
+static int validate_stop_copy_read_parms(struct file *filp, size_t len)
+{
+	struct vfio_ap_migration_data *mig_data;
+	struct ap_matrix_mdev *matrix_mdev;
+	loff_t total_len;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (check_add_overflow((loff_t)len, filp->f_pos, &total_len))
+		return -EIO;
+
+	/*
+	 * matrix_mdev is guaranteed live here: vfio_ap_open_file_stream() took
+	 * a vfio_device registration reference that is held until
+	 * vfio_ap_release_mig_file() runs, so the embedding matrix_mdev cannot
+	 * be freed while this file descriptor is open.
+	 */
+	matrix_mdev = filp->private_data;
+
+	if (!matrix_mdev->mig_data)
+		return -ENODEV;
+
+	mig_data = matrix_mdev->mig_data;
+
+	if (mig_data->stop_copy_mig_file.filp != filp)
+		return -EINVAL;
+
+	return 0;
+}
+
+static size_t vfio_ap_config_size(struct ap_matrix_mdev *matrix_mdev,
+				  unsigned int *num_queues)
+{
+	size_t qinfo_size;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	*num_queues = vfio_ap_mdev_get_num_queues(&matrix_mdev->shadow_apcb);
+	qinfo_size = *num_queues * sizeof(struct vfio_ap_queue_info);
+
+	return qinfo_size + sizeof(struct vfio_ap_config);
+}
+
+static int get_hardware_info_for_queue(const char *mdev_name,
+				       struct ap_tapq_hwinfo *hwinfo,
+				       unsigned long apqn)
+{
+	struct ap_queue_status status;
+
+	status = ap_test_queue(apqn, 1, hwinfo);
+
+	switch (status.response_code) {
+	case AP_RESPONSE_NORMAL:
+	case AP_RESPONSE_RESET_IN_PROGRESS:
+	case AP_RESPONSE_DECONFIGURED:
+	case AP_RESPONSE_CHECKSTOPPED:
+	case AP_RESPONSE_BUSY:
+		/* For all these RCs the tapq info should be available */
+		break;
+	default:
+		pr_err_ratelimited("vfio_ap_mdev %s: Failed to get hwinfo for queue %02lx.%04lx: TAPQ rc=%d\n",
+				   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn),
+				   status.response_code);
+		return -EIO;
+	}
+
+	/* There should be at least one of the mode bits set */
+	if (!hwinfo->value) {
+		pr_err_ratelimited("vfio_ap_mdev %s: Empty hwinfo for queue %02lx.%04lx: TAPQ rc=%d\n",
+				   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn),
+				   status.response_code);
+		return -EIO;
+	}
+
+	return 0;
+}
+
+/**
+ * vfio_ap_store_queue_info:
+ *
+ * Stores the hardware information returned from the PQAP(TAPQ) command for each
+ * queue device identified in the 'qinfo' field of the a vfio_ap_config
+ * object. The APQNs in the 'qinfo' field must already have been snapshotted
+ * prior to calling this function.
+ *
+ * @mdev_name:	The name (UUID) of the mediated device to use in log messages
+ * @ap_config:	A reference to the vfio_ap_config instance in which to store
+ *		the queue information. It is expected that each APQN identifying
+ *		a queue device for which hardware information is to be retrieved
+ *		shall be snapshotted prior to calling this function.
+ *
+ * Returns:	Zero (0) if the hardware information is retrieved for each queue
+ *		device in the AP configuration; otherwise, returns an error.
+ */
+static int vfio_ap_store_queue_info(const char *mdev_name,
+				    struct vfio_ap_config *ap_config)
+{
+	struct ap_tapq_hwinfo source_hwinfo;
+	unsigned long num_queues;
+	int ret;
+
+	for (num_queues = 0; num_queues < ap_config->num_queues; num_queues++) {
+		ret = get_hardware_info_for_queue(mdev_name, &source_hwinfo,
+						  ap_config->qinfo[num_queues].apqn);
+		if (ret)
+			return ret;
+
+		ap_config->qinfo[num_queues].data = source_hwinfo.value;
+	}
+
+	return 0;
+}
+
+static int vfio_ap_get_config(struct ap_matrix_mdev *matrix_mdev)
+{
+	struct vfio_ap_config *ap_configuration;
+	unsigned long *apm, *aqm, apid, apqi;
+	unsigned int num_queues;
+	const char *mdev_name;
+	size_t ap_config_size;
+	int ret, qindex;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	ap_config_size = vfio_ap_config_size(matrix_mdev, &num_queues);
+
+	ap_configuration = kvzalloc(ap_config_size, GFP_KERNEL_ACCOUNT);
+	if (!ap_configuration)
+		return -ENOMEM;
+
+	ap_configuration->magic   = VFIO_AP_MIG_MAGIC;
+	ap_configuration->version = VFIO_AP_MIG_VERSION;
+
+	/*
+	 * num_queues must be set before writing qinfo[] elements; the
+	 * __counted_by(num_queues) annotation on qinfo[] causes the compiler to
+	 * insert bounds checks that evaluate against ap_configuration->num_queues.
+	 * Writing through qinfo[i] with num_queues still 0 would trap.
+	 */
+	ap_configuration->num_queues = num_queues;
+
+	apm = matrix_mdev->shadow_apcb.apm;
+	aqm = matrix_mdev->shadow_apcb.aqm;
+	qindex = 0;
+	for_each_set_bit_inv(apid, apm, AP_DEVICES) {
+		for_each_set_bit_inv(apqi, aqm, AP_DOMAINS) {
+			ap_configuration->qinfo[qindex].apqn =
+				AP_MKQID(apid, apqi);
+			qindex += 1;
+		}
+	}
+	memcpy(ap_configuration->adm, matrix_mdev->shadow_apcb.adm,
+	       sizeof(ap_configuration->adm));
+	mdev_name = dev_name(matrix_mdev->vdev.dev);
+
+	ret = vfio_ap_store_queue_info(mdev_name, ap_configuration);
+	if (ret) {
+		kvfree(ap_configuration);
+		return ret;
+	}
+
+	matrix_mdev->mig_data->stop_copy_mig_file.ap_config = ap_configuration;
+	matrix_mdev->mig_data->stop_copy_mig_file.config_sz = ap_config_size;
+
+	return 0;
+}
+
+static ssize_t vfio_ap_stop_copy_read(struct file *filp, char __user *buf,
+				      size_t len, loff_t *pos)
+{
+	struct vfio_ap_migration_file *mig_file;
+	struct ap_matrix_mdev *matrix_mdev;
+	void *bounce;
+	ssize_t ret;
+
+	/*
+	 * This file was opened with stream_open(), so pos should be NULL for
+	 * sequential read() calls; a non-NULL pointer will be passed only
+	 * for positional pread() calls in which case we return an error
+	 * indicating broken pipe/illegal seek on a non-seekable file
+	 */
+	if (pos)
+		return -ESPIPE;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	pos = &filp->f_pos;
+
+	ret = validate_stop_copy_read_parms(filp, len);
+	if (ret) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return ret;
+	}
+
+	matrix_mdev = filp->private_data;
+	mig_file = &matrix_mdev->mig_data->stop_copy_mig_file;
+
+	/*
+	 * The data to be returned to the caller - i.e., the source guest's
+	 * AP configuration data - is generated on the first read() call. The
+	 * result is cached in mig_file->ap_config for subsequent read() calls.
+	 */
+	if (!mig_file->ap_config) {
+		ret = vfio_ap_get_config(matrix_mdev);
+		if (ret) {
+			mutex_unlock(&matrix_dev->mdevs_lock);
+			return ret;
+		}
+	}
+
+	/* Return EOF if all of the AP configuration data has been read */
+	if (*pos >= mig_file->config_sz) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return 0;
+	}
+
+	/*
+	 * Don't read past the end of the AP configuration data. Limit len to
+	 * the number of bytes remaining.
+	 */
+	len = min_t(size_t, mig_file->config_sz - *pos, len);
+	if (len == 0) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return 0;
+	}
+
+	/*
+	 * Copy into a bounce buffer under mdevs_lock and advance *pos, then
+	 * perform copy_to_user() outside the lock. This avoids stalling
+	 * all host mdev operations if userspace passes a buffer that faults.
+	 */
+	bounce = kmalloc(len, GFP_KERNEL);
+	if (!bounce) {
+		mutex_unlock(&matrix_dev->mdevs_lock);
+		return -ENOMEM;
+	}
+
+	memcpy(bounce, (char *)mig_file->ap_config + *pos, len);
+	*pos += len;
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	if (copy_to_user(buf, bounce, len)) {
+		kfree(bounce);
+		return -EFAULT;
+	}
+
+	kfree(bounce);
+	return len;
+}
+
 static const struct file_operations vfio_ap_stop_copy_fops = {
 	.owner = THIS_MODULE,
 	.read = vfio_ap_stop_copy_read,
-- 
2.53.0

[PATCH v10 08/15] s390/vfio-ap: Transition device migration state from STOP to RESUMING

[Anthony Krowiak]

Transitioning from VFIO_DEVICE_STATE_STOP to VFIO_DEVICE_STATE_RESUMING
starts a process of restoring the device state of the vfio device on the
target system. To prepare for restoring the device state, open a file
stream to receive the guest's AP configuration saved when the device state
on the source system transitioned from VFIO_DEVICE_STATE_STOP to
VFIO_DEVICE_STATE_STOP_COPY.

Note:
This commit introduces the file operations structure for migration state
files with a stub implementation of the write operation. The complete
implementation is provided in the subsequent commit.

This incremental approach allows for easier review of the migration
infrastructure setup separate from the actual implementation logic.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 34 +++++++++++++++++++++++--
 1 file changed, 32 insertions(+), 2 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index f9b00fb89410..9ed657c7302e 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -451,6 +451,26 @@ static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
 	return filp;
 }
 
+static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
+				      size_t len, loff_t *pos)
+{
+	/* TODO */
+	return -EOPNOTSUPP;
+}
+
+static const struct file_operations vfio_ap_resume_fops = {
+	.owner = THIS_MODULE,
+	.write = vfio_ap_resuming_write,
+	.release = vfio_ap_release_mig_file,
+};
+
+static struct file *vfio_ap_resuming_init(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	return vfio_ap_open_file_stream(matrix_mdev, &vfio_ap_resume_fops, O_WRONLY);
+}
+
 static struct file *
 vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 			    enum vfio_device_mig_state new_state)
@@ -482,10 +502,20 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 		return filp;
 	}
 
+	/*
+	 * Begins the process of restoring the vfio device state by creating and
+	 * returning a streaming data_fd to be used to read in the internal
+	 * state of the vfio-ap device on the destination host.
+	 */
 	if (cur_state == VFIO_DEVICE_STATE_STOP &&
 	    new_state == VFIO_DEVICE_STATE_RESUMING) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+		struct file *filp = vfio_ap_resuming_init(matrix_mdev);
+
+		if (IS_ERR(filp))
+			return ERR_CAST(filp);
+
+		mig_data->resuming_mig_file.filp = filp;
+		return filp;
 	}
 
 	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
-- 
2.53.0

[PATCH v10 09/15] s390/vfio-ap: Prepare lock helpers and matrix init for cross-file use

[Anthony Krowiak]

Move get_update_locks_for_mdev() and release_update_locks_for_mdev() from
vfio_ap_ops.c into vfio_ap_private.h as static inline functions so they are
accessible to vfio_ap_migration.c in subsequent patches.

Add assert_has_update_locks_for_mdev() to vfio_ap_private.h for lockdep
validation of these update locks across files.

Make vfio_ap_matrix_init() non-static and add its declaration to
vfio_ap_private.h for the same reason.

No functional change.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_ops.c     | 50 +----------------------
 drivers/s390/crypto/vfio_ap_private.h | 58 +++++++++++++++++++++++++++
 2 files changed, 59 insertions(+), 49 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index 635c8a20af86..a4eed70b05d8 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -88,53 +88,6 @@ static inline void release_update_locks_for_kvm(struct kvm *kvm)
 	mutex_unlock(&matrix_dev->guests_lock);
 }
 
-/**
- * get_update_locks_for_mdev: Acquire the locks required to dynamically update a
- *			      KVM guest's APCB in the proper order.
- *
- * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
- *		 configuration data to use to update a KVM guest's APCB.
- *
- * The proper locking order is:
- * 1. matrix_dev->guests_lock: required to use the KVM pointer to update a KVM
- *			       guest's APCB.
- * 2. matrix_mdev->kvm->lock:  required to update a guest's APCB
- * 3. matrix_dev->mdevs_lock:  required to access data stored in a matrix_mdev
- *
- * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
- *	 lock will not be taken.
- */
-static inline void get_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
-{
-	mutex_lock(&matrix_dev->guests_lock);
-	if (matrix_mdev && matrix_mdev->kvm)
-		mutex_lock(&matrix_mdev->kvm->lock);
-	mutex_lock(&matrix_dev->mdevs_lock);
-}
-
-/**
- * release_update_locks_for_mdev: Release the locks used to dynamically update a
- *				  KVM guest's APCB in the proper order.
- *
- * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
- *		 configuration data to use to update a KVM guest's APCB.
- *
- * The proper unlocking order is:
- * 1. matrix_dev->mdevs_lock
- * 2. matrix_mdev->kvm->lock
- * 3. matrix_dev->guests_lock
- *
- * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
- *	 lock will not be released.
- */
-static inline void release_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
-{
-	mutex_unlock(&matrix_dev->mdevs_lock);
-	if (matrix_mdev && matrix_mdev->kvm)
-		mutex_unlock(&matrix_mdev->kvm->lock);
-	mutex_unlock(&matrix_dev->guests_lock);
-}
-
 /**
  * get_update_locks_by_apqn: Find the mdev to which an APQN is assigned and
  *			     acquire the locks required to update the APCB of
@@ -649,8 +602,7 @@ static int handle_pqap(struct kvm_vcpu *vcpu)
 	return 0;
 }
 
-static void vfio_ap_matrix_init(struct ap_config_info *info,
-				struct ap_matrix *matrix)
+void vfio_ap_matrix_init(struct ap_config_info *info, struct ap_matrix *matrix)
 {
 	matrix->apm_max = info->apxa ? info->na : 63;
 	matrix->aqm_max = info->apxa ? info->nd : 15;
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index c6e577064e7e..1324d94638d8 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -176,4 +176,62 @@ int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev);
 
+/**
+ * get_update_locks_for_mdev: Acquire the locks required to dynamically update a
+ *			      KVM guest's APCB in the proper order.
+ *
+ * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
+ *		 configuration data to use to update a KVM guest's APCB.
+ *
+ * The proper locking order is:
+ * 1. matrix_dev->guests_lock: required to use the KVM pointer to update a KVM
+ *			       guest's APCB.
+ * 2. matrix_mdev->kvm->lock:  required to update a guest's APCB
+ * 3. matrix_dev->mdevs_lock:  required to access data stored in a matrix_mdev
+ *
+ * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
+ *	 lock will not be taken.
+ */
+static inline void get_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
+{
+	mutex_lock(&matrix_dev->guests_lock);
+	if (matrix_mdev && matrix_mdev->kvm)
+		mutex_lock(&matrix_mdev->kvm->lock);
+	mutex_lock(&matrix_dev->mdevs_lock);
+}
+
+/**
+ * release_update_locks_for_mdev: Release the locks used to dynamically update a
+ *				  KVM guest's APCB in the proper order.
+ *
+ * @matrix_mdev: a pointer to a struct ap_matrix_mdev object containing the AP
+ *		 configuration data to use to update a KVM guest's APCB.
+ *
+ * The proper unlocking order is:
+ * 1. matrix_dev->mdevs_lock
+ * 2. matrix_mdev->kvm->lock
+ * 3. matrix_dev->guests_lock
+ *
+ * Note: If @matrix_mdev is NULL or is not attached to a KVM guest, the KVM
+ *	 lock will not be released.
+ */
+static inline void release_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
+{
+	mutex_unlock(&matrix_dev->mdevs_lock);
+	if (matrix_mdev && matrix_mdev->kvm)
+		mutex_unlock(&matrix_mdev->kvm->lock);
+	mutex_unlock(&matrix_dev->guests_lock);
+}
+
+static inline void
+assert_has_update_locks_for_mdev(struct ap_matrix_mdev *matrix_mdev)
+{
+	lockdep_assert_held(&matrix_dev->guests_lock);
+	if (matrix_mdev && matrix_mdev->kvm)
+		lockdep_assert_held(&matrix_mdev->kvm->lock);
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+}
+
+void vfio_ap_matrix_init(struct ap_config_info *info, struct ap_matrix *matrix);
+
 #endif /* _VFIO_AP_PRIVATE_H_ */
-- 
2.53.0

[PATCH v10 10/15] s390/vfio-ap: File ops called to resume the vfio device migration

[Anthony Krowiak]

Implements the 'write' callback function for the file stream created to
restore the state of the vfio-ap device on the destination host during the
RESUMING phase.

Userspace reads the source guest's saved AP configuration metadata from the
STOP_COPY stream and writes it to this stream in chunks. The write callback
accumulates the stream into a pre-allocated vfio_ap_config buffer. Once all
data has arrived, the configuration is validated against the destination
mdev's pre-configured shadow_apcb and hardware capabilities.

In order for the source guest's configuration to be considered compatible:
* The migration data must carry the expected magic number and version.
* Every APQN and control domain in the source configuration must be present
  in the destination mdev's shadow_apcb.
* The hardware facilities and AP type of each queue must be compatible
  between source and destination.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 634 +++++++++++++++++++++++-
 1 file changed, 631 insertions(+), 3 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 9ed657c7302e..469fa09ec908 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -13,6 +13,61 @@
 #define VFIO_AP_MIG_MAGIC			0x76666170U  /* "vfap" */
 #define VFIO_AP_MIG_VERSION			1U
 
+/*
+ * Masks the fields of the queue information returned from the PQAP(TAPQ)
+ * command. In order to migrate a guest, it's AP configuration must be
+ * compatible with AP configuration assigned to the target guest's mdev.
+ * This mask is used to verify that the queue information for each source and
+ * target queue is compatible.
+ *
+ * The following bits must match for the source device and the corresponding
+ * destination device:
+ * -------------------------------------------------------------------------
+ * S bit 0: APSC  facility installed
+ * M bit 1: APQKM facility installed
+ * C bit 2: AP4KC facility installed
+ * Mode bits 3-5:
+ *     D bit 3: CCA-mode facility
+ *     A bit 4: accelerator-mode facility
+ *     X bit 5: XCP-mode facility
+ * N  bit 6: APXA facility installed
+ * SL bit 7: SLCF facility installed
+ *
+ * Either bit 8 or bit 9 will be set. If bit 8 is set for the source device,
+ * then it must also be set for the corresponding destination device:
+ * -------------------------------------------------------------------------
+ * Classification (functional capabilities) bits 8-15
+ *     bit 8: Native card function
+ *     bit 9: Only stateless functions
+ *
+ * The BS bits must be set to 0 for both the source and corresponding
+ * destination device:
+ * -------------------------------------------------------------------------
+ * BS bits 16-17:
+ *
+ * The AP type of the source device must be less than or equal to that of
+ * the corresponding destination device:
+ * -------------------------------------------------------------------------
+ * AP Type bits 32-39:
+ */
+#define QINFO_DATA_MASK		0xffffc000ff000000
+
+/*
+ * Masks the bit that indicates whether full native card function is available
+ * from the 8 bits specifying the functional capabilities of a queue
+ */
+#define CLASSIFICATION_NATIVE_FCN_MASK		0x80
+
+/* The maximum number of queues that can be installed in an s390 system */
+#define MAX_AP_QUEUES				(AP_DEVICES * AP_DOMAINS)
+
+/* The maximum size of a vfio_ap_config blob, used to pre-allocate the receive
+ * buffer on the destination host during the RESUMING phase of migration.
+ */
+#define VFIO_AP_CONFIG_MAX_SIZE \
+	(sizeof(struct vfio_ap_config) + \
+	 MAX_AP_QUEUES * sizeof(struct vfio_ap_queue_info))
+
 /**
  * struct vfio_ap_migration_file
  *
@@ -451,11 +506,562 @@ static struct file *vfio_ap_open_file_stream(struct ap_matrix_mdev *matrix_mdev,
 	return filp;
 }
 
+static int validate_resuming_write_parms(struct file *filp, size_t len)
+{
+	struct vfio_ap_migration_data *mig_data;
+	struct ap_matrix_mdev *matrix_mdev;
+	loff_t total_len;
+
+	lockdep_assert_held(&matrix_dev->mdevs_lock);
+
+	if (!len || filp->f_pos < 0)
+		return -EINVAL;
+
+	if (check_add_overflow((loff_t)len, filp->f_pos, &total_len))
+		return -ERANGE;
+
+	matrix_mdev = filp->private_data;
+	if (!matrix_mdev || !matrix_mdev->mig_data)
+		return -ENODEV;
+
+	mig_data = matrix_mdev->mig_data;
+
+	if (filp != mig_data->resuming_mig_file.filp)
+		return -ENXIO;
+
+	/* Reject writes that would overflow the pre-allocated buffer */
+	if (filp->f_pos + len > VFIO_AP_CONFIG_MAX_SIZE)
+		return -EIO;
+
+	return 0;
+}
+
+static void report_facilities_compatibility(const char *mdev_name,
+					    unsigned long apqn,
+					    struct ap_tapq_hwinfo *src_hwinfo,
+					    struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->apsc != target_hwinfo->apsc) {
+		if (src_hwinfo->apsc) {
+			pr_err_ratelimited("vfio_ap_mdev %s: APSC facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: APSC facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: APSC facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: APSC facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->mex4k != target_hwinfo->mex4k) {
+		if (src_hwinfo->mex4k) {
+			pr_err_ratelimited("vfio_ap_mdev %s: mex4k facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: mex4k facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: mex4k facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: mex4k facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->crt4k != target_hwinfo->crt4k) {
+		if (src_hwinfo->crt4k) {
+			pr_err_ratelimited("vfio_ap_mdev %s: crt4k facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: crt4k facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: crt4k facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: crt4k facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_mode_compatibility(const char *mdev_name,
+				      unsigned long apqn,
+				      struct ap_tapq_hwinfo *src_hwinfo,
+				      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->cca != target_hwinfo->cca) {
+		if (src_hwinfo->cca) {
+			pr_err_ratelimited("vfio_ap_mdev %s: Coprocessor-mode facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: Coprocessor-mode facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: Coprocessor-mode facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: Coprocessor-mode facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->accel != target_hwinfo->accel) {
+		if (src_hwinfo->accel) {
+			pr_err_ratelimited("vfio_ap_mdev %s: Accelerator-mode facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: Accelerator-mode facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: Accelerator-mode facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: Accelerator-mode facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+
+	if (src_hwinfo->ep11 != target_hwinfo->ep11) {
+		if (src_hwinfo->ep11) {
+			pr_err_ratelimited("vfio_ap_mdev %s: XCP-mode facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: XCP-mode facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: XCP-mode facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: XCP-mode facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_apxa_compatibility(const char *mdev_name,
+				      unsigned long apqn,
+				      struct ap_tapq_hwinfo *src_hwinfo,
+				      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->apxa != target_hwinfo->apxa) {
+		if (src_hwinfo->apxa) {
+			pr_err_ratelimited("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility not installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility not installed in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: AP-extended-addressing (APXA) facility installed in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_slcf_compatibility(const char *mdev_name,
+				      unsigned long apqn,
+				      struct ap_tapq_hwinfo *src_hwinfo,
+				      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->slcf != target_hwinfo->slcf) {
+		if (src_hwinfo->slcf) {
+			pr_err_ratelimited("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) available in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) not available in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		} else {
+			pr_err_ratelimited("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) not available in source queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+			pr_err_ratelimited("vfio_ap_mdev %s: Stateless-command-filtering (SLCF) available in target queue %02lx.%04lx\n",
+					   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+		}
+	}
+}
+
+static void report_bs_compatibility(const char *mdev_name,
+				    unsigned long apqn,
+				    struct ap_tapq_hwinfo *src_hwinfo,
+				    struct ap_tapq_hwinfo *target_hwinfo)
+{
+	/*
+	 * The BS field on both the source and destination must be 0, so if one
+	 * of them is not, then report an error.
+	 */
+	if (src_hwinfo->bs || target_hwinfo->bs) {
+		pr_err_ratelimited("vfio_ap_mdev %s: Bind/associate state for source (%01x) and target (%01x) queue %02lx.%04lx must be 0\n",
+				   mdev_name, src_hwinfo->bs, target_hwinfo->bs,
+				   AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+	}
+}
+
+static void report_aptype_compatibility(const char *mdev_name,
+					unsigned long apqn,
+					struct ap_tapq_hwinfo *src_hwinfo,
+					struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (src_hwinfo->at > target_hwinfo->at) {
+		pr_err_ratelimited("vfio_ap_mdev %s: AP type of source queue %02lx.%04lx (%02x) not compatible with target (%02x)\n",
+				   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn),
+				   src_hwinfo->at, target_hwinfo->at);
+	}
+}
+
+static bool classes_compatible(struct ap_tapq_hwinfo *src_hwinfo,
+			       struct ap_tapq_hwinfo *target_hwinfo)
+{
+	unsigned long src_native, target_native;
+
+	src_native = src_hwinfo->class & CLASSIFICATION_NATIVE_FCN_MASK;
+	target_native = target_hwinfo->class & CLASSIFICATION_NATIVE_FCN_MASK;
+
+	/*
+	 * If the source queue has full native card function and the
+	 * target queue has only stateless functions available, then
+	 * there may be instructions that will not execute on the
+	 * target queue. This shall be reported as an error.
+	 *
+	 * If the source queue has only stateless card functions and the
+	 * target queue has full native card function available, then
+	 * we are okay because the target queue can run all stateless card
+	 * functions.
+	 */
+	return (src_native != target_native) ? !src_native : true;
+}
+
+static void report_class_compatibility(const char *mdev_name,
+				       unsigned long apqn,
+				       struct ap_tapq_hwinfo *src_hwinfo,
+				       struct ap_tapq_hwinfo *target_hwinfo)
+{
+	if (!classes_compatible(src_hwinfo, target_hwinfo)) {
+		pr_err_ratelimited("vfio_ap_mdev %s: Full native card function available on source queue %02lx.%04lx\n",
+				   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+		pr_err_ratelimited("vfio_ap_mdev %s: Only stateless functions available on target queue %02lx.%04lx\n",
+				   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+	}
+}
+
+/*
+ * Log a device error reporting that migration failed due to queue
+ * incompatibilities followed by a device error for each incompatible feature.
+ */
+static void report_qinfo_incompatibilities(const char *mdev_name,
+					   unsigned long apqn,
+					   struct ap_tapq_hwinfo *src_hwinfo,
+					   struct ap_tapq_hwinfo *target_hwinfo)
+{
+	pr_err_ratelimited("vfio_ap_mdev %s: Migration failed: Source and target queue (%02lx.%04lx) not compatible\n",
+			   mdev_name, AP_QID_CARD(apqn), AP_QID_QUEUE(apqn));
+
+	report_facilities_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_mode_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_apxa_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_slcf_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_aptype_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_bs_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+	report_class_compatibility(mdev_name, apqn, src_hwinfo, target_hwinfo);
+}
+
+/**
+ * queue_hardware_info_is_compatible:
+ *
+ * Verify whether the hardware information for a source queue is compatible with
+ * the hardware info for the corresponding queue on this system.
+ *
+ * In order to be compatible, the hardware information for each queue must
+ * meet the following requirements:
+ *
+ * 1. The hardware facilities bits much match
+ * 2. The AP type of the source queue must be the same as or older than that
+ *    of the target queue (target is backwards compatible)
+ * 3. The classification bits must indicate:
+ *    - Both queues have full native card function or both have stateless
+ *      functions available
+ *    - If the classification bits don't match, then the only acceptable
+ *      configuration is stateless functions for the source queue and
+ *      full native function for the target queue
+ * 4. The BS bits for both queues must be 0 (Queue usable for all messages
+ *    supported by the adapter)
+ *
+ * @mdev_name:	The mdev name to use in error messages
+ * @apqn:	The APQN for the queues
+ * @src_hwinfo: The hardware info for the source queue
+ * @target_hwinfo: The hardware info for the corresponding queue on this system
+ *
+ * Returns: true if the hardware info for the two queues is compatible;
+ *          otherwise, returns false.
+ */
+static bool queue_hardware_info_is_compatible(const char *mdev_name,
+					      unsigned long apqn,
+					      struct ap_tapq_hwinfo *src_hwinfo,
+					      struct ap_tapq_hwinfo *target_hwinfo)
+{
+	unsigned long src_bits, target_bits;
+
+	src_bits = src_hwinfo->value & QINFO_DATA_MASK;
+	target_bits = target_hwinfo->value & QINFO_DATA_MASK;
+
+	/* If all bits match the queues are compatible */
+	if (src_bits == target_bits &&
+	    (src_hwinfo->bs == 0 && target_hwinfo->bs == 0))
+		return true;
+
+	if (src_hwinfo->apsc  == target_hwinfo->apsc     &&
+	    src_hwinfo->mex4k == target_hwinfo->mex4k    &&
+	    src_hwinfo->crt4k == target_hwinfo->crt4k    &&
+	    src_hwinfo->cca   == target_hwinfo->cca      &&
+	    src_hwinfo->accel == target_hwinfo->accel    &&
+	    src_hwinfo->ep11  == target_hwinfo->ep11     &&
+	    src_hwinfo->slcf  == target_hwinfo->slcf     &&
+	    src_hwinfo->apxa  == target_hwinfo->apxa     &&
+	    src_hwinfo->at    <= target_hwinfo->at       &&
+	    classes_compatible(src_hwinfo, target_hwinfo) &&
+	    (src_hwinfo->bs == 0 && target_hwinfo->bs == 0))
+		return true;
+
+	report_qinfo_incompatibilities(mdev_name, apqn, src_hwinfo, target_hwinfo);
+
+	return false;
+}
+
+/**
+ * verify_ap_configs_are_compatible:
+ *
+ * Verifies that the queues in the source guest's AP configuration are
+ * compatible with the corresponding queues on this system.
+ *
+ * @mdev_name:	   The mdev name to use in error messages
+ * @source_config: The object specifying the source guest's AP configuration
+ *
+ * Returns: an error indicating either a failure to retrieve a queue's
+ *			hardware information or one or more source queues are not
+ *			compatible with the corresponding queue on this system; otherwise,
+ *			returns zero to indicate compatibility.
+ */
+static int verify_ap_configs_are_compatible(const char *mdev_name,
+					    struct vfio_ap_config *source_config)
+{
+	struct ap_tapq_hwinfo src_hwinfo, dest_hwinfo;
+	unsigned long apqn;
+	int ret = 0, rc;
+
+	for (int i = 0; i < source_config->num_queues; i++) {
+		apqn = source_config->qinfo[i].apqn;
+
+		/*
+		 * If we can't get the hardware info for a particular queue, then let's
+		 * capture the function return code and continue so we can log all
+		 * errors to aid in debugging of migration.
+		 */
+		rc = get_hardware_info_for_queue(mdev_name, &dest_hwinfo, apqn);
+		if (rc) {
+			ret = rc;
+			continue;
+		}
+
+		src_hwinfo.value =  source_config->qinfo[i].data;
+
+		if (!queue_hardware_info_is_compatible(mdev_name, apqn,
+						       &src_hwinfo,
+						       &dest_hwinfo))
+			ret = -EINVAL;
+	}
+
+	return ret;
+}
+
+/**
+ * ap_config_is_subset_of_shadow_apcb:
+ *
+ * Verify that each APQN and control domain in the source guest's AP
+ * configuration is present in the destination mdev's shadow_apcb. The
+ * destination mdev must be pre-configured by the administrator with at least
+ * the adapters, domains and control domains the source guest is actively
+ * using. Since shadow_apcb is derived from the administrator's assignment
+ * filtered to only installed and vfio_ap-bound queues, any APQN or control
+ * domain present in shadow_apcb is guaranteed to be available.
+ *
+ * All missing APQNs and control domains are logged before returning so the
+ * administrator sees all problems at once rather than one per retry.
+ *
+ * @mdev_name:     The mdev name to use in error messages
+ * @matrix_mdev:   The destination mdev whose shadow_apcb to check against
+ * @source_config: The source guest's AP configuration
+ *
+ * Returns: true if every APQN and control domain in @source_config is present
+ *          in @matrix_mdev->shadow_apcb; otherwise returns false.
+ */
+static bool ap_config_is_subset_of_shadow_apcb(const char *mdev_name,
+					       struct ap_matrix_mdev *matrix_mdev,
+					       struct vfio_ap_config *source_config)
+{
+	unsigned long apid, apqi, apqn, domain_num;
+	bool ret = true;
+
+	for (int i = 0; i < source_config->num_queues; i++) {
+		apqn = source_config->qinfo[i].apqn;
+		apid = AP_QID_CARD(apqn);
+		apqi = AP_QID_QUEUE(apqn);
+
+		if (!test_bit_inv(apid, matrix_mdev->shadow_apcb.apm) ||
+		    !test_bit_inv(apqi, matrix_mdev->shadow_apcb.aqm)) {
+			pr_err_ratelimited("vfio_ap_mdev %s: Queue %02lx.%04lx not in destination mdev's AP configuration\n",
+					   mdev_name, apid, apqi);
+			ret = false;
+		}
+	}
+
+	for_each_set_bit_inv(domain_num, (unsigned long *)source_config->adm,
+			     AP_DOMAINS) {
+		if (!test_bit_inv(domain_num, matrix_mdev->shadow_apcb.adm)) {
+			pr_err_ratelimited("vfio_ap_mdev %s: Control domain %04lx not in destination mdev's AP configuration\n",
+					   mdev_name, domain_num);
+			ret = false;
+		}
+	}
+
+	return ret;
+}
+
+static int do_post_copy_validation(struct ap_matrix_mdev *matrix_mdev,
+				   struct vfio_ap_config *source_config)
+{
+	const char *mdev_name = dev_name(matrix_mdev->vdev.dev);
+
+	if (source_config->magic != VFIO_AP_MIG_MAGIC ||
+	    source_config->version != VFIO_AP_MIG_VERSION)
+		return -EINVAL;
+
+	if (!ap_config_is_subset_of_shadow_apcb(mdev_name, matrix_mdev,
+						source_config))
+		return -EINVAL;
+
+	return verify_ap_configs_are_compatible(mdev_name, source_config);
+}
+
+static int do_post_copy_processing(struct ap_matrix_mdev *matrix_mdev,
+				   struct vfio_ap_config *ap_config)
+{
+	lockdep_assert_held(&ap_attr_mutex);
+	assert_has_update_locks_for_mdev(matrix_mdev);
+
+	return do_post_copy_validation(matrix_mdev, ap_config);
+}
+
 static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
 				      size_t len, loff_t *pos)
 {
-	/* TODO */
-	return -EOPNOTSUPP;
+	struct ap_matrix_mdev *matrix_mdev;
+	struct vfio_ap_config *ap_config;
+	ssize_t ret;
+	void *kbuf;
+
+	/*
+	 * This file was opened with stream_open(), so pos should be NULL for
+	 * sequential write() calls; a non-NULL pointer will be passed only
+	 * for positional pwrite() calls in which case we return an error
+	 * indicating broken pipe/illegal seek on a non-seekable file.
+	 */
+	if (pos)
+		return -ESPIPE;
+
+	/*
+	 * Reject absurd lengths before allocating the bounce buffer below.
+	 * This only caps the allocation: a write can never be larger than
+	 * the receive buffer. The authoritative check against the space
+	 * remaining is made by validate_resuming_write_parms() under the
+	 * locks.
+	 */
+	if (len > VFIO_AP_CONFIG_MAX_SIZE)
+		return -EIO;
+
+	/*
+	 * Copy the user data into a kernel buffer before taking any locks.
+	 * copy_from_user() can fault and block for an unbounded time, which
+	 * must not happen while holding ap_attr_mutex, guests_lock, kvm->lock
+	 * or mdevs_lock.
+	 */
+	kbuf = vmemdup_user(buf, len);
+	if (IS_ERR(kbuf))
+		return PTR_ERR(kbuf);
+
+	/*
+	 * Hold ap_attr_mutex for the full duration of the write, just as
+	 * (un)assign_adapter_store() and (un)assign_domain_store() do.  This
+	 * prevents the AP bus apmask/aqmask attributes from being changed
+	 * while the guest's AP configuration is being updated.
+	 *
+	 * get_update_locks_for_mdev() then acquires guests_lock, kvm->lock,
+	 * and mdevs_lock in the correct order. This serialises
+	 * the entire operation against concurrent AP attribute writers
+	 * while the guest's AP configuration is being changed.
+	 *
+	 * Holding these locks for the full duration of a potentially chunked
+	 * write could in theory affect performance, but this is acceptable for
+	 * several reasons: migration is an infrequent operation; real-world
+	 * guest AP configurations are small (each CEX8 card has 2 adapters and
+	 * up to 16 domains, and the 85 cards in a system are shared across all
+	 * LPARs and guests); and only a memcpy() and some integer checks are
+	 * done for each chunk while the locks are held.
+	 */
+	matrix_mdev = filp->private_data;
+	mutex_lock(&ap_attr_mutex);
+	get_update_locks_for_mdev(matrix_mdev);
+	pos = &filp->f_pos;
+
+	ret = validate_resuming_write_parms(filp, len);
+	if (ret)
+		goto out_unlock;
+
+	ap_config = matrix_mdev->mig_data->resuming_mig_file.ap_config;
+
+	memcpy((char *)ap_config + *pos, kbuf, len);
+	*pos += len;
+
+	/*
+	 * Check whether we have received all the data.  We know the total
+	 * expected size once num_queues has arrived, i.e. once *pos is past
+	 * the fixed header.  Until then keep accumulating.
+	 */
+	if (*pos >= offsetofend(struct vfio_ap_config, num_queues)) {
+		size_t expected_sz;
+
+		if (ap_config->num_queues > MAX_AP_QUEUES) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+
+		expected_sz = sizeof(struct vfio_ap_config) +
+			      ap_config->num_queues *
+			      sizeof(struct vfio_ap_queue_info);
+
+		if (*pos > (loff_t)expected_sz) {
+			ret = -EINVAL;
+			goto out_unlock;
+		}
+
+		if (*pos == (loff_t)expected_sz) {
+			ret = do_post_copy_processing(matrix_mdev, ap_config);
+			matrix_mdev->mig_data->resuming_mig_data_complete = !ret;
+		}
+	}
+
+out_unlock:
+	release_update_locks_for_mdev(matrix_mdev);
+	mutex_unlock(&ap_attr_mutex);
+	kvfree(kbuf);
+	return ret ? ret : (ssize_t)len;
 }
 
 static const struct file_operations vfio_ap_resume_fops = {
@@ -466,9 +1072,31 @@ static const struct file_operations vfio_ap_resume_fops = {
 
 static struct file *vfio_ap_resuming_init(struct ap_matrix_mdev *matrix_mdev)
 {
+	struct vfio_ap_config *ap_config;
+	struct file *filp;
+
 	lockdep_assert_held(&matrix_dev->mdevs_lock);
 
-	return vfio_ap_open_file_stream(matrix_mdev, &vfio_ap_resume_fops, O_WRONLY);
+	/*
+	 * Pre-allocate the maximum possible receive buffer so that
+	 * vfio_ap_resuming_write() can copy directly into it without needing
+	 * to know num_queues up front.  kvzalloc falls back to vmalloc for
+	 * large allocations rather than failing a high-order kmalloc.
+	 */
+	ap_config = kvzalloc(VFIO_AP_CONFIG_MAX_SIZE, GFP_KERNEL_ACCOUNT);
+	if (!ap_config)
+		return ERR_PTR(-ENOMEM);
+
+	filp = vfio_ap_open_file_stream(matrix_mdev, &vfio_ap_resume_fops, O_WRONLY);
+	if (IS_ERR(filp)) {
+		kvfree(ap_config);
+		return filp;
+	}
+
+	matrix_mdev->mig_data->resuming_mig_file.ap_config = ap_config;
+	matrix_mdev->mig_data->resuming_mig_file.config_sz = VFIO_AP_CONFIG_MAX_SIZE;
+
+	return filp;
 }
 
 static struct file *
-- 
2.53.0

[PATCH v10 11/15] s390/vfio-ap: Transition device migration state to from/to STOP

[Anthony Krowiak]

VFIO_DEVICE_STATE_RESUMING to VFIO_DEVICE_STATE_STOP
VFIO_DEVICE_STATE_STOP_COPY to VFIO_DEVICE_STATE_STOP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Terminates the data transfer session of the vfio-ap device state
between the source and target hosts. Release the migration file
state (ap_config buffers and file pointers) so that a subsequent
migration captures a fresh AP configuration rather than serving
stale data. Since the vfio-ap device does not virtualize a DMA
device, there is no internal device state to incorporate into the
vfio-ap device on the target, so return NULL since no file stream
is needed in the STOP state.

VFIO_DEVICE_STATE_STOP to VFIO_DEVICE_STATE_RUNNING
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Migration has been cancelled. Release the migration file state so
that a subsequent migration captures a fresh AP configuration
rather than serving stale data.

VFIO_DEVICE_STATE_RUNNING to VFIO_DEVICE_STATE_STOP
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Migration has not yet been initiated. No migration file state
exists to release, so just return NULL.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 66 ++++++++++++++++---------
 1 file changed, 44 insertions(+), 22 deletions(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 469fa09ec908..cf38407d1b15 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -196,6 +196,8 @@ static void vfio_ap_release_resuming_file(struct vfio_ap_migration_data *mig_dat
 	mig_data->resuming_mig_data_complete = false;
 }
 
+static void vfio_ap_release_mig_files(struct ap_matrix_mdev *matrix_mdev);
+
 static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 {
 	struct ap_matrix_mdev *matrix_mdev = filp->private_data;
@@ -939,6 +941,9 @@ static int do_post_copy_validation(struct ap_matrix_mdev *matrix_mdev,
 {
 	const char *mdev_name = dev_name(matrix_mdev->vdev.dev);
 
+	lockdep_assert_held(&ap_attr_mutex);
+	assert_has_update_locks_for_mdev(matrix_mdev);
+
 	if (source_config->magic != VFIO_AP_MIG_MAGIC ||
 	    source_config->version != VFIO_AP_MIG_VERSION)
 		return -EINVAL;
@@ -950,15 +955,6 @@ static int do_post_copy_validation(struct ap_matrix_mdev *matrix_mdev,
 	return verify_ap_configs_are_compatible(mdev_name, source_config);
 }
 
-static int do_post_copy_processing(struct ap_matrix_mdev *matrix_mdev,
-				   struct vfio_ap_config *ap_config)
-{
-	lockdep_assert_held(&ap_attr_mutex);
-	assert_has_update_locks_for_mdev(matrix_mdev);
-
-	return do_post_copy_validation(matrix_mdev, ap_config);
-}
-
 static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
 				      size_t len, loff_t *pos)
 {
@@ -1052,7 +1048,7 @@ static ssize_t vfio_ap_resuming_write(struct file *filp, const char __user *buf,
 		}
 
 		if (*pos == (loff_t)expected_sz) {
-			ret = do_post_copy_processing(matrix_mdev, ap_config);
+			ret = do_post_copy_validation(matrix_mdev, ap_config);
 			matrix_mdev->mig_data->resuming_mig_data_complete = !ret;
 		}
 	}
@@ -1146,20 +1142,46 @@ vfio_ap_transition_to_state(struct ap_matrix_mdev *matrix_mdev,
 		return filp;
 	}
 
-	if ((cur_state == VFIO_DEVICE_STATE_RESUMING &&
-	     new_state == VFIO_DEVICE_STATE_STOP) ||
-	    (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
-	     new_state == VFIO_DEVICE_STATE_STOP)) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+	/*
+	 * Terminates the data transfer session of the vfio-ap device state
+	 * to the destination guest.
+	 */
+	if (cur_state == VFIO_DEVICE_STATE_RESUMING &&
+	    new_state == VFIO_DEVICE_STATE_STOP) {
+		if (!mig_data->resuming_mig_data_complete)
+			return ERR_PTR(-EINVAL);
+
+		/* Set resuming_mig_data_complete to false for clean reuse */
+		matrix_mdev->mig_data->resuming_mig_data_complete = false;
+		vfio_ap_release_resuming_file(matrix_mdev->mig_data);
+		return NULL;
+	}
+
+	/*
+	 * Terminates the transfer session of the vfio-ap device state from
+	 * the source guest.
+	 */
+	if (cur_state == VFIO_DEVICE_STATE_STOP_COPY &&
+	    new_state == VFIO_DEVICE_STATE_STOP) {
+		vfio_ap_release_stop_copy_file(matrix_mdev->mig_data);
+		return NULL;
+	}
+
+	/*
+	 * These states indicate migration has either not been initiated or
+	 * has completed and the vfio-ap device is operating normally. Since the
+	 * vfio-ap device does not virtualize a DMA device, there is no internal
+	 * device state to incorporate into the vfio-ap device on the target.
+	 */
+	if (cur_state == VFIO_DEVICE_STATE_STOP &&
+	    new_state == VFIO_DEVICE_STATE_RUNNING) {
+		vfio_ap_release_mig_files(matrix_mdev);
+		return NULL;
 	}
 
-	if ((cur_state == VFIO_DEVICE_STATE_STOP &&
-	     new_state == VFIO_DEVICE_STATE_RUNNING) ||
-	    (cur_state == VFIO_DEVICE_STATE_RUNNING &&
-	     new_state == VFIO_DEVICE_STATE_STOP)) {
-		/* TODO */
-		return ERR_PTR(-EOPNOTSUPP);
+	if (cur_state == VFIO_DEVICE_STATE_RUNNING &&
+	    new_state == VFIO_DEVICE_STATE_STOP) {
+		return NULL;
 	}
 
 	/* vfio_mig_get_next_state() does not use arcs other than the above */
-- 
2.53.0

[PATCH v10 12/15] s390/vfio-ap: Callback to get the size of data to be migrated during guest migration

[Anthony Krowiak]

Callback to get the estimated data length of the data that will be required
to complete reading of the vfio device's internal state. It's mandatory for
VFIO_DEVICE_FEATURE_MIGRATION migration support.

The function pointer for this callback is specified via the
'migration_get_data_size' field of the 'vfio_migration_ops' structure
which is stored with the VFIO device when the 'vfio_device'
structure representing the mediated device is initialized.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index cf38407d1b15..38098968eaa2 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -1278,7 +1278,15 @@ static int vfio_ap_get_state(struct vfio_device *vdev,
 static int vfio_ap_get_data_size(struct vfio_device *vdev,
 				 unsigned long *stop_copy_length)
 {
-	return -EOPNOTSUPP;
+	struct ap_matrix_mdev *matrix_mdev;
+	int num_queues;
+
+	mutex_lock(&matrix_dev->mdevs_lock);
+	matrix_mdev = container_of(vdev, struct ap_matrix_mdev, vdev);
+	*stop_copy_length = vfio_ap_config_size(matrix_mdev, &num_queues);
+	mutex_unlock(&matrix_dev->mdevs_lock);
+
+	return 0;
 }
 
 static const struct vfio_migration_ops vfio_ap_migration_ops = {
-- 
2.53.0

[PATCH v10 13/15] s390/vfio-ap: Set up for vfio-ap device migration

[Anthony Krowiak]

In order to facilitate vfio-ap device migration:

* The function pointers to the callbacks used to facilitate migration of a
  vfio-ap device must be plugged in. These function pointers are specified
  via the fields contained in a struct vfio_migration_ops instance:

  	migration_set_state: Set the migration state of the vfio-ap device
  	migration_get_state: Get the migration state of the vfio-ap device
  	migration_get_data_size: Get the estimated data number bytes of
  				 data that will be required to complete
  				 STOP_COPY
* The migration_flags field of the struct vfio_device instance is set to
  VFIO_MIGRATION_STOP_COPY to indicate that STOP, STOP_COPY and RESUMING
  are the migration states supported for vfio-ap device migration.

* The initial migration state of the vfio-ap device is set to RUNNING

* The boolean flag indicating that all data sent from userspace during the
  RESUMINMG phase has been received is initialized to false.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_migration.c | 24 ++++++++++++++++++++++++
 drivers/s390/crypto/vfio_ap_ops.c       | 10 ++++++++++
 drivers/s390/crypto/vfio_ap_private.h   |  1 +
 3 files changed, 35 insertions(+)

diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 38098968eaa2..660b5a21fe9e 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -212,6 +212,30 @@ static int vfio_ap_release_mig_file(struct inode *file_inode, struct file *filp)
 	return 0;
 }
 
+static const struct vfio_migration_ops vfio_ap_migration_ops;
+
+/**
+ * vfio_ap_setup_vfio_device_migration:
+ *
+ * Plug the object containing the function pointers to the migration callbacks
+ * required to facilitate VFIO AP migration into the mdev
+ *
+ *
+ * @matrix_mdev: pointer to object containing the mdev state
+ */
+void vfio_ap_setup_vfio_device_migration(struct ap_matrix_mdev *matrix_mdev)
+{
+	/*
+	 * Live guest migration is not supported for SE guests, so there is no
+	 * need to initialize the migration capabilities.
+	 */
+	if (ap_is_se_guest())
+		return;
+
+	matrix_mdev->vdev.migration_flags = VFIO_MIGRATION_STOP_COPY;
+	matrix_mdev->vdev.mig_ops = &vfio_ap_migration_ops;
+}
+
 /**
  * validate_stop_copy_read_parms: Validate the input parameters to the
  *                                vfio_ap_stop_copy_read function
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index a4eed70b05d8..ee24297d7b38 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -763,9 +763,19 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 
 	matrix_mdev = vfio_alloc_device(ap_matrix_mdev, vdev, &mdev->dev,
 					&vfio_ap_matrix_dev_ops);
+
 	if (IS_ERR(matrix_mdev))
 		return PTR_ERR(matrix_mdev);
 
+	/*
+	 * Wet up vfio-ap device migration before calling
+	 * vfio_register_emulated_iommu_dev; otherwise, the VFIO core
+	 * will see mig_ops as NULL during the registration. This could
+	 * prevent the VFIO core from properly setting up migration
+	 * infrastructure like debugfs entries.
+	 */
+	vfio_ap_setup_vfio_device_migration(matrix_mdev);
+
 	ret = vfio_register_emulated_iommu_dev(&matrix_mdev->vdev);
 	if (ret)
 		goto err_put_vdev;
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 1324d94638d8..d44188f12221 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -173,6 +173,7 @@ void vfio_ap_on_scan_complete(struct ap_config_info *new_config_info,
 			      struct ap_config_info *old_config_info);
 
 int vfio_ap_init_migration_data(struct ap_matrix_mdev *matrix_mdev);
+void vfio_ap_setup_vfio_device_migration(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_release_migration_data(struct ap_matrix_mdev *matrix_mdev);
 void vfio_ap_reset_migration_state(struct ap_matrix_mdev *matrix_mdev);
 
-- 
2.53.0

[PATCH v10 14/15] s390/vfio-ap: Add 'migration' feature to sysfs 'features' attribute

[Anthony Krowiak]

Add the 'migration' feature to the features provided by the sysfs
/sys/devices/vfio_ap/matrix/feature attribute to indicate that migration
of vfio devices is supported. Since live guest migration is not supported
for SE guests, the 'migration' feature will not be included when the
feature attribute is displayed.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 drivers/s390/crypto/vfio_ap_drv.c | 14 +++++++++++++-
 1 file changed, 13 insertions(+), 1 deletion(-)

diff --git a/drivers/s390/crypto/vfio_ap_drv.c b/drivers/s390/crypto/vfio_ap_drv.c
index 8e69ed286bb9..c63a050a2356 100644
--- a/drivers/s390/crypto/vfio_ap_drv.c
+++ b/drivers/s390/crypto/vfio_ap_drv.c
@@ -26,9 +26,21 @@ MODULE_LICENSE("GPL v2");
 struct ap_matrix_dev *matrix_dev;
 debug_info_t *vfio_ap_dbf_info;
 
+#define VFIO_AP_BASE_FEATURES	"guest_matrix hotplug ap_config"
+#define VFIO_AP_SE_EXCLUDED_FEATURES "migration"
+
 static ssize_t features_show(struct device *dev, struct device_attribute *attr, char *buf)
 {
-	return sysfs_emit(buf, "guest_matrix hotplug ap_config\n");
+	/*
+	 * SE guests do not support live guest migration; emit only the base
+	 * feature set for them.
+	 */
+	if (ap_is_se_guest())
+		return sysfs_emit(buf, "%s\n", VFIO_AP_BASE_FEATURES);
+
+	/* Non-SE: base features plus those not available on SE guests */
+	return sysfs_emit(buf, "%s %s\n", VFIO_AP_BASE_FEATURES,
+			  VFIO_AP_SE_EXCLUDED_FEATURES);
 }
 static DEVICE_ATTR_RO(features);
 
-- 
2.53.0

[PATCH v10 15/15] s390/vfio-ap: Add live guest migration chapter to vfio-ap.rst

[Anthony Krowiak]

Add a 'Live Guest Migration' chapter to the
Documentation/arch/s390/vfio-ap.rst document to describe the details for
initiating live guest migration for a guest to which AP adapters, domains
and control domains have been passed through.

Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
---
 Documentation/arch/s390/vfio-ap.rst     | 641 ++++++++++++++++++++----
 drivers/s390/crypto/vfio_ap_migration.c |   3 +-
 drivers/s390/crypto/vfio_ap_ops.c       |   2 +-
 3 files changed, 545 insertions(+), 101 deletions(-)

diff --git a/Documentation/arch/s390/vfio-ap.rst b/Documentation/arch/s390/vfio-ap.rst
index ac0c07f76ddd..f5d9e3287503 100644
--- a/Documentation/arch/s390/vfio-ap.rst
+++ b/Documentation/arch/s390/vfio-ap.rst
@@ -1012,7 +1012,7 @@ guest_matrix dyn ap_config
 
 the following features are advertised:
 
----------------+---------------------------------------------------------------+
++--------------+---------------------------------------------------------------+
 | Flag         | Description                                                   |
 +==============+===============================================================+
 | guest_matrix | guest_matrix attribute exists. It reports the matrix of       |
@@ -1021,105 +1021,548 @@ the following features are advertised:
 +--------------+---------------------------------------------------------------+
 | dyn          | Indicates hot plug/unplug of AP adapters, domains and control |
 |              | domains for a guest to which the mdev is attached.            |
-+------------+-----------------------------------------------------------------+
++--------------+---------------------------------------------------------------+
 | ap_config    | ap_config interface for one-shot modifications to mdev config |
 +--------------+---------------------------------------------------------------+
+| migration    | Indicates that live guest migration is supported for guests   |
+|              | to which crypto devices are passed through                    |
++--------------+---------------------------------------------------------------+
 
-Limitations
-===========
-Live guest migration is not supported for guests using AP devices without
-intervention by a system administrator. Before a KVM guest can be migrated,
-the vfio_ap mediated device must be removed. Unfortunately, it can not be
-removed manually (i.e., echo 1 > /sys/devices/vfio_ap/matrix/$UUID/remove) while
-the mdev is in use by a KVM guest. If the guest is being emulated by QEMU,
-its mdev can be hot unplugged from the guest in one of two ways:
-
-1. If the KVM guest was started with libvirt, you can hot unplug the mdev via
-   the following commands:
-
-      virsh detach-device <guestname> <path-to-device-xml>
-
-      For example, to hot unplug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 from
-      the guest named 'my-guest':
-
-         virsh detach-device my-guest ~/config/my-guest-hostdev.xml
-
-            The contents of my-guest-hostdev.xml:
-
-.. code-block:: xml
-
-            <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
-              <source>
-                <address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
-              </source>
-            </hostdev>
-
-
-      virsh qemu-monitor-command <guest-name> --hmp "device-del <device-id>"
-
-      For example, to hot unplug the vfio_ap mediated device identified on the
-      qemu command line with 'id=hostdev0' from the guest named 'my-guest':
-
-.. code-block:: sh
-
-         virsh qemu-monitor-command my-guest --hmp "device_del hostdev0"
-
-2. A vfio_ap mediated device can be hot unplugged by attaching the qemu monitor
-   to the guest and using the following qemu monitor command:
-
-      (QEMU) device-del id=<device-id>
-
-      For example, to hot unplug the vfio_ap mediated device that was specified
-      on the qemu command line with 'id=hostdev0' when the guest was started:
-
-         (QEMU) device-del id=hostdev0
-
-After live migration of the KVM guest completes, an AP configuration can be
-restored to the KVM guest by hot plugging a vfio_ap mediated device on the target
-system into the guest in one of two ways:
-
-1. If the KVM guest was started with libvirt, you can hot plug a matrix mediated
-   device into the guest via the following virsh commands:
-
-   virsh attach-device <guestname> <path-to-device-xml>
-
-      For example, to hot plug mdev 62177883-f1bb-47f0-914d-32a22e3a8804 into
-      the guest named 'my-guest':
-
-         virsh attach-device my-guest ~/config/my-guest-hostdev.xml
-
-            The contents of my-guest-hostdev.xml:
-
-.. code-block:: xml
-
-            <hostdev mode='subsystem' type='mdev' managed='no' model='vfio-ap'>
-              <source>
-                <address uuid='62177883-f1bb-47f0-914d-32a22e3a8804'/>
-              </source>
-            </hostdev>
-
-
-   virsh qemu-monitor-command <guest-name> --hmp \
-   "device_add vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
-
-      For example, to hot plug the vfio_ap mediated device
-      62177883-f1bb-47f0-914d-32a22e3a8804 into the guest named 'my-guest' with
-      device-id hostdev0:
-
-      virsh qemu-monitor-command my-guest --hmp \
-      "device_add vfio-ap,\
-      sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
-      id=hostdev0"
-
-2. A vfio_ap mediated device can be hot plugged by attaching the qemu monitor
-   to the guest and using the following qemu monitor command:
-
-      (qemu) device_add "vfio-ap,sysfsdev=<path-to-mdev>,id=<device-id>"
-
-      For example, to plug the vfio_ap mediated device
-      62177883-f1bb-47f0-914d-32a22e3a8804 into the guest with the device-id
-      hostdev0:
+Live Guest Migration
+====================
+The VFIO AP mediated device is not used to provide userspace with direct
+access to device memory as is the case with other devices that use the VFIO
+framework for device pass-through. Instead, it manages AP
+configuration metadata identifying the adapters, domains, and control
+domains to which a guest will be granted access. These AP resources are
+configured by assigning them to a vfio-ap mediated device via its sysfs
+assignment interfaces. When the guest is started, the vfio_ap device driver
+sets the guest's AP configuration from the metadata stored with the mediated
+device. The AP devices are not accessed directly through the vfio_ap driver,
+so the driver does not migrate the state of the AP devices themselves.
+Instead, it migrates the AP configuration metadata. The vfio_ap device
+driver on the destination host will then ensure that the AP configuration
+metadata migrated from the source host is compatible with the AP
+configuration available on the destination host and if
+so, will set the destination guest's AP configuration accordingly.
 
-         (QEMU) device-add "vfio-ap,\
-         sysfsdev=/sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804,\
-         id=hostdev0"
+To be considered compatible, the AP configuration for the destination host must
+meet these requirements:
+
+* Each AP adapter, domain and control domain number assigned to the source
+  guest's AP configuration must be in the destination host's AP
+  configuration. This can be verified as follows:
+
+  * On the source host, display the AP configuration of the source guest
+    with the following two commands:
+
+    .. code-block:: bash
+
+       cat /sys/devices/vfio_ap/matrix/$UUID/guest_matrix
+       cat /sys/devices/vfio_ap/matrix/$UUID/control_domains
+
+    .. note::
+       Replace ``$UUID`` with the actual UUID of your mediated device.
+
+       The ``guest_matrix`` lists the APQNs of the queue devices assigned
+       to the mediated device; for example:
+
+       .. code-block:: bash
+
+          00.0033
+          00.003a
+
+       The ``control_domains`` lists the domain numbers of the control
+       domains; for example:
+
+       .. code-block:: bash
+
+          0033
+          003a
+
+  * Display the AP configuration of the destination host with the following
+    two commands:
+
+    .. code-block:: bash
+
+       lszcrypt -V
+       cat /sys/bus/ap/ap_control_domain_mask
+
+    .. note::
+       The ``lszcrypt -V`` command lists the AP cards (adapters) and queue
+       devices on the host system; for example:
+
+       .. code-block:: bash
+
+          =========== ===== ============ ==========
+          CARD.DOMAIN TYPE  MODE         DRIVER
+          =========== ===== ============ ==========
+          00          CEX5C CCA-Coproc   cex4card
+          00.0033     CEX5C CCA-Coproc   vfio_ap
+          00.003a     CEX5C CCA-Coproc   vfio_ap
+          =========== ===== ============ ==========
+
+       Each bit in the ap_control_domain_mask corresponds to
+       domain numbers 0-255. If a bit is set to one, then
+       the control domain is available on the destination host. For
+       example:
+
+       .. code-block:: bash
+
+          0x0000000000001020000000000000000000000000000000000000000000000000
+
+       This mask indicates that AP control domains 51 (0x33) and 58 (0x3a) are
+       in the AP configuration of the host system.
+
+  * Verify the configurations:
+
+    * Each APQN in the guest's sysfs ``guest_matrix`` file must match an
+      APQN returned from the ``lszcrypt -V`` command on the destination host. It
+      is important to note the driver to which the queue is bound which
+      is displayed in the ``driver`` column. Queues not bound to the vfio_ap
+      driver are not available to the destination guest. Even if the APQNs are
+      available to the driver, that does not guarantee they can be used by the
+      guest being migrated; for example, migration will fail if any of these APQNs
+      are assigned to a mediated device other than the one being migrated.
+
+    * Each domain number from the source guest's sysfs
+      ``control_domains`` attribute must correspond to a bit set to one in
+      the destination host's ``ap_control_domain_mask``.
+
+
+* Each APQN assigned to the source guest and destination guest must
+  reference a queue device with compatible hardware capabilities:
+
+  +--------------+---------------------------------------------------------------+
+  | Hardware     | Description                                                   |
+  | Capabilities |                                                               |
+  +==============+===============================================================+
+  | [1]          | * AP special command facility (APSC)                          |
+  | Facilities   | * AP 4096-bit ME PKU commands facility (AP4KM)                |
+  |              | * AP 4096-bit CRT PKU commands (AP4KC)                        |
+  +--------------+---------------------------------------------------------------+
+  | [1] Mode     | * CCA-mode                                                    |
+  |              | * Accelerator-mode                                            |
+  |              | * XCP-mode (EP11)                                             |
+  +--------------+---------------------------------------------------------------+
+  | [1] AP       |   APXA installed                                              |
+  | extended     |                                                               |
+  | addressing   |                                                               |
+  +--------------+---------------------------------------------------------------+
+  | [1] Command  |   Command filtering available                                 |
+  | filtering    |                                                               |
+  +--------------+---------------------------------------------------------------+
+  | [2]          | * Full native card function                                   |
+  | Functional   | * Only stateless functions                                    |
+  | capabilities |                                                               |
+  +--------------+---------------------------------------------------------------+
+  | [3] AP type  | * 10 (0x0a): CEX4                                             |
+  |              | * 11 (0x0b): CEX5                                             |
+  |              | * 12 (0x0c)  CEX6                                             |
+  |              | * 13 (0x0d)  CEX7                                             |
+  |              | * 14 (0x0e)  CEX8                                             |
+  +--------------+---------------------------------------------------------------+
+
+  +-----------------------------------------------------------------------------+
+  | Table Keys                                                                  |
+  +=============================================================================+
+  |                                                                             |
+  | [1]        The hardware capability must be the same for both the source     |
+  |            and destination queue device.                                    |
+  |                                                                             |
+  | [2]        The source and destination queues must either both have          |
+  |            full native card function or both have stateless functions.      |
+  |            If the functional capabilities don't match, then the source      |
+  |            queue can have stateless capabilities since full native card     |
+  |            function can handle stateless functions; otherwise, migration    |
+  |            will fail.                                                       |
+  |                                                                             |
+  | [3]        The AP type on the source and destination guests can             |
+  |            differ if the queue passed through to the target guest is a      |
+  |            newer model (backwards compatible)                               |
+  +-----------------------------------------------------------------------------+
+
+  * To verify the hardware capabilities are compatible:
+
+    * On both the source and destination hosts, display the hardware capabilities
+      for each AP adapter in the AP configuration for that host:
+
+      .. code-block:: bash
+
+         cat /sys/bus/ap/devices/card$APID/ap_functions
+
+      .. note::
+         The ``$APID`` is the two-character adapter number in hexadecimal format;
+         for example, ``card02`` or ``card1f``. The ``/sys/bus/ap/devices`` directory
+         also lists the APQNs of the queue devices installed in the respective
+         host system with the first two characters being the APID; for example:
+         ``02.0004`` or ``00.0033`` .
+
+    * Verify the hardware capabilities for each AP adapter device on the source
+      and destination host are compatible. The ``ap_functions`` attribute is a
+      bitmask. The bits in the mask read from left to right starting with bit 0.
+      Each bit that is set to one indicates the corresponding hardware capability
+      is installed:
+
+      * Bits 0-2 are the facilities bits. Each bit value must match for the AP
+        devices on the source and destination systems. The values indicate the
+        following:
+
+        * bit-0: APSC is installed
+        * bit-1: AP4KM is installed
+        * bit-2: AP4KC is installed
+
+      * Bits 3-5 specify the adapter Modes. Only one of these bits will be set to
+        one and must be the same for both the source and destination adapter
+        devices:
+
+        * bit-3: CCA-mode
+        * bit-4: Accelerator-mode
+        * bit-5: XCP-mode (EP11)
+
+      * Bit 6 specifies whether APXA is installed and must be the same for both
+        the source and destination adapter devices.
+
+      * Bit 7 specifies whether command filtering is installed
+        and must be the same for both the source and destination adapter devices.
+
+      * Bits 8-15 are the classification bits. There are only two relevant
+        bits and only one of them will be set to one. For the source and destination
+        adapter devices to be considered compatible:
+
+        * Bit 8 may be set to 1 on both hosts (full native card function)
+        * Bit 9 may be set to 1 on both hosts (only stateless functions available)
+        * Bit 9 may be set to 1 on the source host and bit 8 may be set to 1 on
+          the destination host
+
+      * Bits 16-17 are the binding state bits which must be 00
+
+  * To verify the AP types are compatible:
+
+    * On both the source and destination hosts, display the hardware type
+      for each AP adapter in the AP configuration for that host to ensure the
+      source and destination adapter types are the same, or the source type is
+      less than the destination type::
+
+       cat /sys/bus/ap/devices/card$APID/hwtype
+
+      .. note::
+         The ``$APID`` is the two-character adapter number in hexadecimal format;
+         for example, ``card02`` or ``card1f``.
+
+Setting up for live guest migration on the destination host
+-----------------------------------------------------------
+To set up a host as the destination for live guest migration, do the
+following:
+
+1. Create a mediated device
+~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Create a mediated device with the same name (UUID) as the mediated device
+used to supply the AP configuration to the source guest. For example, if
+the mediated device on the source guest is named
+62177883-f1bb-47f0-914d-32a22e3a8804:
+
+.. code-block:: bash
+
+   echo 62177883-f1bb-47f0-914d-32a22e3a8804 > \
+     /sys/devices/vfio_ap/matrix/mdev_supported_types/vfio_ap-passthrough/create
+
+2. Reserve adapters and domains for the vfio_ap device driver's use
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Reserve the same adapters and domains passed through to the source guest
+for the vfio_ap device driver on the destination host by clearing the
+adapter numbers from the ``/sys/bus/ap/apmask`` and/or the domain numbers
+from the ``/sys/bus/ap/aqmask`` files.
+
+For example, suppose adapters 0, 20 (0x14) and 22 (0x16) as well as
+domains 51 (0x33) and 58 (0x3a) are passed through to the source guest. To
+ensure they can be passed through to the destination guest, they must be
+made available to the vfio_ap device driver on the destination host. To
+make them available, do one or both of the following on the destination host:
+
+.. code-block:: bash
+
+   echo -0,-0x14,-22 > /sys/bus/ap/apmask
+   echo -0,-0x33,-0x3a > /sys/bus/ap/aqmask
+
+.. note::
+
+    * It is not necessary to reserve both the adapters and domains.
+      Reserving an adapter implicitly allows the vfio_ap driver to assign
+      each of the domains available on the system along with the reserved
+      adapters to a guest's AP configuration and vice versa.
+
+    * The Cartesian product of the adapters and domains reserved for the
+      vfio_ap device driver identifies the APQNs of the AP queue devices to be
+      bound to the vfio_ap device driver. If an APQN does not reference a
+      queue device installed in the system at the time of live guest migration,
+      the migration will fail.
+
+    * To verify that the queue devices are reserved for the vfio_ap
+      device driver, issue the ``lszcrypt -V`` command and you should
+      see ``vfio_ap`` in the ``DRIVER`` column of the output.
+
+3. Assign adapters, domains and control domains to the destination mediated device
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Assign the same adapters, domains and control domains to the destination
+mediated device as are assigned to the source guest's mediated device. For
+example, using the same adapters, domains and control domains from the
+previous step:
+
+.. code-block:: bash
+
+   echo 0x0 > /sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804/assign_adapter
+   echo 0x14 > /sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804/assign_adapter
+   echo 0x16 > /sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804/assign_adapter
+   echo 0x33 > /sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804/assign_domain
+   echo 0x3a > /sys/devices/vfio_ap/matrix/62177883-f1bb-47f0-914d-32a22e3a8804/assign_domain
+
+.. note::
+
+    * The destination mediated device must be configured with at least the
+      adapters, domains and control domains that are actively in use by the
+      source guest (i.e., present in the source mdev's AP configuration
+      shadow). Migration will fail if any APQN or control domain from the
+      source guest's AP configuration is not present in the destination
+      mdev's AP configuration shadow.
+
+    * The destination mediated device may be configured with a superset of
+      the source guest's active AP configuration. Any additionally assigned
+      resources that are available on the destination host will be accessible
+      to the guest after migration completes.
+
+Live guest migration failures due to AP configuration errors
+------------------------------------------------------------
+This section describes the errors that may occur during live guest migration
+when the AP configuration of the source guest and destination host are not
+compatible and where to look for problem determination.
+
+The destination host is missing the mediated device
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+This error occurs when a mediated device with the same name (UUID) as the
+mediated device being migrated has not been created on the destination host.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: device not found: mediated device '$UUID' not           |
+|              | found                                                          |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | initiating migration                                           |
+|              | qemu-system-s390x: Sibling indicated error 1                   |
++--------------+----------------------------------------------------------------+
+
+.. note::
+   $UUID is the UUID of the mediated device being migrated from the source host.
+
+
+One or more queues are not bound to the vfio_ap driver on the destination host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The queue devices passed through to the source guest are not installed in the
+destination host or are not bound to its vfio_ap device driver.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: No such device: Failed to load vmstate version_id: 1,  |
+|              | ret: -19                                                       |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Kernel log:  | vfio_ap_mdev $UUID: Queue $APID.$APQI not available to         |
+|              | vfio_ap driver on target host                                  |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | shutting down, reason=failed                                   |
+|              | qemu-system-s390x: terminating on signal $SIGNAL_NUM from      |
+|              | pid $PID $DAEMON                                               |
++--------------+----------------------------------------------------------------+
+
+
+One or more control domains are not available on the destination host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The control domains passed through to the source guest are not installed on the
+destination host.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: No such device: Failed to load vmstate version_id: 1,  |
+|              | ret: -19                                                       |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Kernel log:  | vfio_ap_mdev $UUID: Control domain $DOMAIN_NUM not available   |
+|              | on the destination host                                        |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | shutting down, reason=failed                                   |
+|              | qemu-system-s390x: terminating on signal $SIGNAL_NUM from      |
+|              | pid $PID $DAEMON                                               |
++--------------+----------------------------------------------------------------+
+
+
+.. note::
+   * $UUID is the UUID of the mediated device being migrated from the source host.
+   * $APID.$APQI is adapter number and queue index (domain number) comprising the
+     $APQN (for example, 00.0033) of the queue device that is not available.
+   * $SIGNAL_NUM is the signal number that caused the QEMU process to terminate.
+   * $PID is the process ID of the QEMU process on the destination host.
+   * $DAEMON is the name of the QEMU daemon process.
+   * This message will be logged for each queue for which this error is detected.
+
+Failure to get hardware information for a queue device on destination host
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The vfio_ap device driver on the destination host will execute an AP instruction
+to get the hardware information for a queue device to perform queue compatibility
+checks. The instruction can fail for a number of reasons in which case the
+migration will be terminated.
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: failed to get hardware information for queue device    |
+|              | $APQN                                                          |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | vfio_ap_mdev $UUID: Failed to get hwinfo for queue $APQN:      |
+|              | TAPQ rc=$RESPONSE-CODE                                         |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | shutting down, reason=failed                                   |
+|              | qemu-system-s390x: terminating on signal $SIGNAL-ID from pid   |
+|              | $PID $DAEMON                                                   |
++--------------+----------------------------------------------------------------+
+
+.. note::
+   * $UUID is the UUID of the mediated device being migrated from the source host.
+   * $APQN (for example, 00.0033) of the queue device that is not compatible.
+   * $RESPONSE_CODE is the response code from the AP instruction.
+   * $SIGNAL_NUM is the signal number of the signal that caused the QEMU process
+     to terminate.
+   * $PID is the process ID of the QEMU process on the destination host.
+   * $DAEMON is the name of the QEMU daemon process.
+   * This message will be logged for each queue for which this error is detected.
+
+The AP configurations of the source guest and destination host not compatible
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+The functional capabilities or facilities available on one or more of the queues
+passed through to the source guest are not compatible with the queue device with
+the same APQN on the destination system (see the Hardware Capabilities table above)
+
+**Source host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | error: operation failed: migration failed. Message from the    |
+|              | source host: operation failed: job 'migration out' failed:     |
+|              | Sibling indicated error 1. Message from the destination host:  |
+|              | operation failed: job 'migration in' failed: load of migration |
+|              | failed: Invalid argument: Failed to load vmstate               |
+|              | version_id: 1, ret: -22                                        |
++--------------+----------------------------------------------------------------+
+| Kernel log:  | N/A                                                            |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | *initiating migration*                                         |
+|              |                                                                |
+|              | *qemu-system-s390x: Sibling indicated error 1*                 |
++--------------+----------------------------------------------------------------+
+
+**Destination host**
+
++--------------+----------------------------------------------------------------+
+| Log          | Message                                                        |
++==============+================================================================+
+| Console log: | N/A                                                            |
++--------------+----------------------------------------------------------------+
+| Kernel log:  | *vfio_ap_mdev $UUID: Migration failed: Source and target       |
+|              | queue ($APQN) not compatible*                                  |
+|              |                                                                |
+|              | The message above will be followed by one or more messages     |
+|              | enumerating the incompatible features; for example:            |
+|              |                                                                |
+|              | ``vfio_ap_mdev $UUID: APSC facility installed in source queue  |
+|              | $APQN``                                                        |
+|              | ``vfio_ap_mdev $UUID: APSC facility not installed in target    |
+|              | queue $APQN``                                                  |
+|              |                                                                |
+|              | ``vfio_ap_mdev $UUID: AP type of source queue $APQN ($APTYPE1) |
+|              | not compatible with target ($APTYPE2)`` ...                    |
++--------------+----------------------------------------------------------------+
+| QEMU log:    | *initiating migration*                                         |
+|              |                                                                |
+|              | *qemu-system-s390x: error while loading state section id ...*  |
+|              |                                                                |
+|              | *shutting down, reason=failed*                                 |
+|              |                                                                |
+|              | *terminating on signal $SIGNAL-ID from pid $PID $DAEMON*       |
++--------------+----------------------------------------------------------------+
+
+.. note::
+   * $UUID is the UUID of the mediated device being migrated from the source host.
+   * $APQN (for example, 00.0033) of the queue device that is incompatible.
+   * $APTYPE1 is the type of the source queue device.
+   * $APTYPE2 is the type of the target queue device.
+   * $SIGNAL-ID is the signal number of the signal that caused the QEMU process
+     to terminate.
+   * $PROCESS-ID is the process ID of the QEMU process on the source host.
+   * $PID is the process ID of the QEMU process on the destination host.
+   * $DAEMON is the name of the QEMU daemon process.
+   * Each follow-on message logging the incompatibility will be logged for each
+     error detected for the specified queue device.
+
+AP Configuration Management
+---------------------------
+The AP configurations of the source guest and destination host must be kept
+in synchronization or live guest migration will likely fail due to potential
+incompatibilities introduced by such changes. In particular, changing adapter
+or domain reservations via the sysfs ``apmask`` or ``aqmask`` attributes on
+either the source or destination host without coordinating such changes between
+the two hosts -especially while a migration is taking place - can result in
+migration failures.
+
+Configuration stability is an orchestration-layer or system administrator
+responsibility, which is consistent with other VFIO device types. The vfio_ap
+device driver will validate source and destination configurations and provide
+clear diagnostics when incompatibilities are detected, enabling orchestration
+tools to implement appropriate policies; for example, blocking migration when
+such changes are to be made.
+
+Master Key administration
+--------------------------
+It is imperative that s390 Common Cryptographic Architecture (CCA) master key
+administration be performed on both the source and destination AP
+devices to synchronize the key values prior to allowing live guest
+migration. If the master keys do not match, then crypto applications that
+rely on secure keys wrapped by a CCA master key will fail when the guest on
+which they are running is migrated to the destination host. Again, this is
+an orchestration-layer or system administrator responsibility and migration must
+be blocked while master key administration is being performed.
diff --git a/drivers/s390/crypto/vfio_ap_migration.c b/drivers/s390/crypto/vfio_ap_migration.c
index 660b5a21fe9e..ac135872da2f 100644
--- a/drivers/s390/crypto/vfio_ap_migration.c
+++ b/drivers/s390/crypto/vfio_ap_migration.c
@@ -217,8 +217,9 @@ static const struct vfio_migration_ops vfio_ap_migration_ops;
 /**
  * vfio_ap_setup_vfio_device_migration:
  *
+ * Enable
  * Plug the object containing the function pointers to the migration callbacks
- * required to facilitate VFIO AP migration into the mdev
+ * used to facilitate migration of a vfio-ap device.
  *
  *
  * @matrix_mdev: pointer to object containing the mdev state
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index ee24297d7b38..e049c4141a53 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -768,7 +768,7 @@ static int vfio_ap_mdev_probe(struct mdev_device *mdev)
 		return PTR_ERR(matrix_mdev);
 
 	/*
-	 * Wet up vfio-ap device migration before calling
+	 * Setting up for vfio device migration must be done before calling
 	 * vfio_register_emulated_iommu_dev; otherwise, the VFIO core
 	 * will see mig_ops as NULL during the registration. This could
 	 * prevent the VFIO core from properly setting up migration
-- 
2.53.0