[PATCH v2 17/26] iommu/amd: Pass KVM FD from userspace when initializing vIOMMU

[Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>]

AMD HW-vIOMMU feature requires IOMMU driver to keep track of each guest.
This information is used by AMD IOMMU driver to manage the following:

* GID: Each  guest is assigned a unique 16-bit Guest ID (GID), which is
used to index into various data structures for configuring the hardware.

* Translation-devid: Each guest has one GPA->SPA mapping, which requires
one trans_devid to program the v1 page table in the DTE[trans_devid].

* Extended interrupt remapping: The AMD HW-vIOMMU uses AVIC to implement
extended interrupt remapping to virtualize Event/PPR log interrupts.
A KVM reference is neeed to get the AVIC vm_id.

The KVM FD can be used for these purposes.

Signed-off-by: Suravee Suthikulpanit <suravee.suthikulpanit@amd.com>
---
 drivers/iommu/amd/amd_iommu_types.h |  2 ++
 drivers/iommu/amd/iommufd.c         | 27 ++++++++++++++++++++++++++-
 include/uapi/linux/iommufd.h        |  2 ++
 3 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/amd/amd_iommu_types.h b/drivers/iommu/amd/amd_iommu_types.h
index 836d5cd08134..e9b49f0b9051 100644
--- a/drivers/iommu/amd/amd_iommu_types.h
+++ b/drivers/iommu/amd/amd_iommu_types.h
@@ -547,6 +547,8 @@ struct amd_iommu_viommu {
 	struct protection_domain *parent; /* nest parent domain for this viommu */
 	struct list_head pdom_list;	  /* For protection_domain->viommu_list */
 	u16 gid;			  /* Guest ID for the vIOMMU */
+	u32 kvmfd;			  /* KVM fd from VMM */
+	void *kvm;			  /* Hold struct kvm pointer */
 
 	/*
 	 * Per-vIOMMU guest domain ID to host domain ID mapping.
diff --git a/drivers/iommu/amd/iommufd.c b/drivers/iommu/amd/iommufd.c
index 6020f2caf445..7c7ef267088b 100644
--- a/drivers/iommu/amd/iommufd.c
+++ b/drivers/iommu/amd/iommufd.c
@@ -4,6 +4,8 @@
  */
 
 #include <linux/iommu.h>
+#include <linux/file.h>
+#include <linux/amd-iommu.h>
 
 #include "iommufd.h"
 #include "amd_iommu.h"
@@ -42,13 +44,27 @@ size_t amd_iommufd_get_viommu_size(struct device *dev, enum iommu_viommu_type vi
 	return VIOMMU_STRUCT_SIZE(struct amd_iommu_viommu, core);
 }
 
+static void *get_kvm_handler(u32 kvmfd)
+{
+	struct fd f;
+
+	f = fdget(kvmfd);
+
+	if (fd_empty(f)) {
+		pr_warn("%s: fdget failed\n", __func__);
+		return NULL;
+	}
+
+	return fd_file(f)->private_data;
+}
+
 int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *parent,
 			    const struct iommu_user_data *user_data)
 {
 	int ret;
 	phys_addr_t page_base;
 	unsigned long flags;
-	struct iommu_viommu_amd data;
+	struct iommu_viommu_amd data = {};
 	struct protection_domain *pdom = to_pdomain(parent);
 	struct amd_iommu *iommu = container_of(viommu->iommu_dev, struct amd_iommu, iommu);
 	struct amd_iommu_viommu *aviommu = container_of(viommu, struct amd_iommu_viommu, core);
@@ -81,6 +97,13 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
 
 	aviommu->vfmmio_mmap_offset = data.out_vfmmio_mmap_offset;
 
+	aviommu->kvm = get_kvm_handler(data.kvmfd);
+	if (aviommu->kvm == NULL) {
+		pr_err("%s: Failed to get KVM handler (kvmfd=%#x)\n", __func__, data.kvmfd);
+		ret = -EINVAL;
+		goto err_kvmfd;
+	}
+
 	/* Reset vIOMMU MMIOs to initialize the vIOMMU */
 	iommu_reset_vmmio(iommu, aviommu->gid);
 
@@ -94,6 +117,7 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
 	if (ret)
 		goto err_init;
 
+	aviommu->kvmfd = data.kvmfd;
 	viommu->ops = &amd_viommu_ops;
 
 	spin_lock_irqsave(&pdom->lock, flags);
@@ -102,6 +126,7 @@ int amd_iommufd_viommu_init(struct iommufd_viommu *viommu, struct iommu_domain *
 
 	return 0;
 err_init:
+err_kvmfd:
 	iommufd_viommu_destroy_mmap(&aviommu->core, aviommu->vfmmio_mmap_offset);
 err_mmap:
 	amd_iommu_gid_free(iommu, aviommu->gid);
diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 0b7a3e5b057c..69aa44bba95a 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -1085,10 +1085,12 @@ struct iommu_viommu_tegra241_cmdqv {
 /**
  * struct iommu_viommu_amd - AMD vIOMMU Interface (IOMMU_VIOMMU_TYPE_AMD)
  * @out_vfmmio_mmap_offset: (out) mmap offset for vIOMMU VF-MMIO
+ * @kvmfd: KVM FD handler
  * @reserved: Must be zero
  */
 struct iommu_viommu_amd {
 	__aligned_u64 out_vfmmio_mmap_offset;
+	__u32 kvmfd;
 	__u32 reserved; /* must be last */
 };
 
-- 
2.34.1