Re: [PATCH v7 02/15] s390/vfio-ap: Data structures for facilitating vfio device migration

[Anthony Krowiak <akrowiak@linux.ibm.com>]

On 8/10/26 9:45 AM, Jason J. Herne wrote:
>
>
> On 8/7/26 6:18 PM, Anthony Krowiak wrote:
>> Creates the data structures used to facilitate state transitions during
>> vfio device migration.
>>
>> Signed-off-by: Anthony Krowiak <akrowiak@linux.ibm.com>
>> ---
>>   drivers/s390/crypto/Makefile            |   2 +-
>>   drivers/s390/crypto/vfio_ap_migration.c | 113 ++++++++++++++++++++++++
>>   drivers/s390/crypto/vfio_ap_private.h   |   5 ++
>>   3 files changed, 119 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..374d3a67cb21
>> --- /dev/null
>> +++ b/drivers/s390/crypto/vfio_ap_migration.c
>> @@ -0,0 +1,113 @@
>> +// 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_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;
>> +    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 comprise of a 
>> large number of
>
> Typo. I think you wanted 'comprised' here.

I did, thanks.

>
> Reviewed-by: Jason J. Herne <jjherne@linux.ibm.com>
>