[RFC PATCH v1 07/38] iommufd/viommu: Add support to associate viommu with kvm instance

Aneesh Kumar K.V (Arm)
2025-07-28T13:53:18Z

The associated kvm instance will be used in later patch by iommufd to
bind a tdi to kvm.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
drivers/iommu/iommufd/viommu.c | 45 +++++++++++++++++++++++++++++++++-
include/linux/iommufd.h | 3 +++
include/uapi/linux/iommufd.h | 12 +++++++++
3 files changed, 59 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/iommufd/viommu.c b/drivers/iommu/iommufd/viommu.c
index 2ca5809b238b..59f1e1176f7f 100644
--- a/drivers/iommu/iommufd/viommu.c
+++ b/drivers/iommu/iommufd/viommu.c
@@ -2,6 +2,36 @@
/* Copyright (c) 2024, NVIDIA CORPORATION & AFFILIATES
*/
#include "iommufd_private.h"
+#include "linux/tsm.h"
+
+#if IS_ENABLED(CONFIG_KVM)
+#include <linux/kvm_host.h>
+
+static int viommu_get_kvm(struct iommufd_viommu *viommu, int kvm_vm_fd)
+{
+ int rc = -EBADF;
+ struct file *filp;
+
+ filp = fget(kvm_vm_fd);
+
+ if (!file_is_kvm(filp))
+ goto err_out;
+
+ /* hold the kvm reference via file descriptor */
+ viommu->kvm_filp = filp;
+ return 0;
+err_out:
+ viommu->kvm_filp = NULL;
+ fput(filp);
+ return rc;
+}
+
+static void viommu_put_kvm(struct iommufd_viommu *viommu)
+{
+ fput(viommu->kvm_filp);
+ viommu->kvm_filp = NULL;
+}
+#endif

void iommufd_viommu_destroy(struct iommufd_object *obj)
{
@@ -12,6 +42,8 @@ void iommufd_viommu_destroy(struct iommufd_object *obj)
viommu->ops->destroy(viommu);
refcount_dec(&viommu->hwpt->common.obj.users);
xa_destroy(&viommu->vdevs);
+
+ viommu_put_kvm(viommu);
}

int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
@@ -29,7 +61,9 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
size_t viommu_size;
int rc;

- if (cmd->flags || cmd->type == IOMMU_VIOMMU_TYPE_DEFAULT)
+ if (cmd->flags & ~IOMMU_VIOMMU_KVM_FD)
+ return -EOPNOTSUPP;
+ if (cmd->type == IOMMU_VIOMMU_TYPE_DEFAULT)
return -EOPNOTSUPP;

idev = iommufd_get_device(ucmd, cmd->dev_id);
@@ -100,8 +134,17 @@ int iommufd_viommu_alloc_ioctl(struct iommufd_ucmd *ucmd)
goto out_put_hwpt;
}

+ /* get the kvm details if specified. */
+ if (cmd->flags & IOMMU_VIOMMU_KVM_FD) {
+ rc = viommu_get_kvm(viommu, cmd->kvm_vm_fd);
+ if (rc)
+ goto out_put_hwpt;
+ }
+
cmd->out_viommu_id = viommu->obj.id;
rc = iommufd_ucmd_respond(ucmd, sizeof(*cmd));
+ if (rc)
+ viommu_put_kvm(viommu);

out_put_hwpt:
iommufd_put_object(ucmd->ictx, &hwpt_paging->common.obj);
diff --git a/include/linux/iommufd.h b/include/linux/iommufd.h
index 55ae02581f9b..b7617ba7a536 100644
--- a/include/linux/iommufd.h
+++ b/include/linux/iommufd.h
@@ -12,6 +12,7 @@
#include <linux/refcount.h>
#include <linux/types.h>
#include <linux/xarray.h>
+#include <linux/file.h>
#include <uapi/linux/iommufd.h>

struct device;
@@ -58,6 +59,7 @@ struct iommufd_object {
unsigned int id;
};

+struct kvm;
struct iommufd_device *iommufd_device_bind(struct iommufd_ctx *ictx,
struct device *dev, u32 *id);
void iommufd_device_unbind(struct iommufd_device *idev);
@@ -102,6 +104,7 @@ struct iommufd_viommu {
struct iommufd_ctx *ictx;
struct iommu_device *iommu_dev;
struct iommufd_hwpt_paging *hwpt;
+ struct file *kvm_filp;

const struct iommufd_viommu_ops *ops;

diff --git a/include/uapi/linux/iommufd.h b/include/uapi/linux/iommufd.h
index 548d4b5afcd4..9014c61a97d4 100644
--- a/include/uapi/linux/iommufd.h
+++ b/include/uapi/linux/iommufd.h
@@ -1023,6 +1023,17 @@ struct iommu_viommu_tegra241_cmdqv {
__aligned_u64 out_vintf_mmap_length;
};

+/**
+ * define IOMMU_VIOMMU_KVM_FD - Flag indicating a valid KVM VM file descriptor
+ *
+ * This flag must be set when allocating a viommu instance that will be
+ * associated with a specific KVM VM. When allocating a viommu instance for a
+ * KVM VM, this flag must be set to inform the initialization logic that
+ * @iommu_viommu_alloc::kvm_vm_fd is properly initialized. If this flag is not
+ * provided but @iommu_viommu_alloc::kvm_vm_fd field will be ignored.
+ */
+#define IOMMU_VIOMMU_KVM_FD BIT(0)
+
/**
* struct iommu_viommu_alloc - ioctl(IOMMU_VIOMMU_ALLOC)
* @size: sizeof(struct iommu_viommu_alloc)
@@ -1057,6 +1068,7 @@ struct iommu_viommu_alloc {
__u32 data_len;
__u32 __reserved;
__aligned_u64 data_uptr;
+ __u32 kvm_vm_fd;
};
#define IOMMU_VIOMMU_ALLOC _IO(IOMMUFD_TYPE, IOMMUFD_CMD_VIOMMU_ALLOC)

--
2.43.0