Re: [PATCH 1/2] vfio: selftests: Add support of creating multiple iommus from iommufd

[David Matlack <dmatlack@google.com>]

On 2026-05-05 10:14 PM, Samiullah Khawaja wrote:
> IOMMUFD allows creating multiple IOAS and HWPTs under one iommufd, Add
> API to init a struct iommu using an already opened iommufd. The API
> internally creates a new IOAS and also a new HWPT as an option based on
> the flags passed to the function.
> 
> Signed-off-by: Samiullah Khawaja <skhawaja@google.com>
> ---
>  .../vfio/lib/include/libvfio/iommu.h          |  5 ++
>  .../lib/include/libvfio/vfio_pci_device.h     |  2 +
>  tools/testing/selftests/vfio/lib/iommu.c      | 62 +++++++++++++++++--
>  .../selftests/vfio/lib/vfio_pci_device.c      | 22 ++++++-
>  4 files changed, 84 insertions(+), 7 deletions(-)
> 
> diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h b/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h
> index e9a3386a4719..89249a294920 100644
> --- a/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h
> +++ b/tools/testing/selftests/vfio/lib/include/libvfio/iommu.h
> @@ -9,6 +9,9 @@
>  
>  typedef u64 iova_t;
>  
> +/* Create IOMMU with page tables */
> +#define IOMMUFD_IOMMU_INIT_CREATE_PT 1
> +
>  struct iommu_mode {
>  	const char *name;
>  	const char *container_path;
> @@ -29,10 +32,12 @@ struct iommu {
>  	int container_fd;
>  	int iommufd;
>  	u32 ioas_id;
> +	u32 hwpt_id;
>  	struct list_head dma_regions;
>  };
>  
>  struct iommu *iommu_init(const char *iommu_mode);
> +struct iommu *iommufd_iommu_init(int iommufd, u32 dev_id, u32 flags);
>  void iommu_cleanup(struct iommu *iommu);
>  
>  int __iommu_map(struct iommu *iommu, struct dma_region *region);
> diff --git a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
> index 2858885a89bb..1143ceb6a9b8 100644
> --- a/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
> +++ b/tools/testing/selftests/vfio/lib/include/libvfio/vfio_pci_device.h
> @@ -19,6 +19,7 @@ struct vfio_pci_device {
>  	const char *bdf;
>  	int fd;
>  	int group_fd;
> +	u32 dev_id;

Please introduce an initialize this field in its own patch and, in the
commit message, explain why it is being added and  how it will be used.

>  
>  	struct iommu *iommu;
>  
> @@ -65,6 +66,7 @@ void vfio_pci_config_access(struct vfio_pci_device *device, bool write,
>  #define vfio_pci_config_writew(_d, _o, _v) vfio_pci_config_write(_d, _o, _v, u16)
>  #define vfio_pci_config_writel(_d, _o, _v) vfio_pci_config_write(_d, _o, _v, u32)
>  
> +void vfio_pci_device_attach_iommu(struct vfio_pci_device *device, struct iommu *iommu);
>  void vfio_pci_irq_enable(struct vfio_pci_device *device, u32 index,
>  			 u32 vector, int count);
>  void vfio_pci_irq_disable(struct vfio_pci_device *device, u32 index);
> diff --git a/tools/testing/selftests/vfio/lib/iommu.c b/tools/testing/selftests/vfio/lib/iommu.c
> index 035dac069d60..644c049cf9f0 100644
> --- a/tools/testing/selftests/vfio/lib/iommu.c
> +++ b/tools/testing/selftests/vfio/lib/iommu.c
> @@ -408,6 +408,18 @@ struct iommu_iova_range *iommu_iova_ranges(struct iommu *iommu, u32 *nranges)
>  	return ranges;
>  }
>  
> +static u32 iommufd_hwpt_alloc(struct iommu *iommu, u32 dev_id)
> +{
> +	struct iommu_hwpt_alloc args = {
> +		.size = sizeof(args),
> +		.pt_id = iommu->ioas_id,
> +		.dev_id = dev_id,
> +	};
> +
> +	ioctl_assert(iommu->iommufd, IOMMU_HWPT_ALLOC, &args);
> +	return args.out_hwpt_id;
> +}
> +
>  static u32 iommufd_ioas_alloc(int iommufd)
>  {
>  	struct iommu_ioas_alloc args = {
> @@ -418,11 +430,9 @@ static u32 iommufd_ioas_alloc(int iommufd)
>  	return args.out_ioas_id;
>  }
>  
> -struct iommu *iommu_init(const char *iommu_mode)
> +static struct iommu *iommu_alloc(const char *iommu_mode)
>  {
> -	const char *container_path;
>  	struct iommu *iommu;
> -	int version;
>  
>  	iommu = calloc(1, sizeof(*iommu));
>  	VFIO_ASSERT_NOT_NULL(iommu);
> @@ -430,6 +440,16 @@ struct iommu *iommu_init(const char *iommu_mode)
>  	INIT_LIST_HEAD(&iommu->dma_regions);
>  
>  	iommu->mode = lookup_iommu_mode(iommu_mode);
> +	return iommu;
> +}
> +
> +struct iommu *iommu_init(const char *iommu_mode)
> +{
> +	const char *container_path;
> +	struct iommu *iommu;
> +	int version;
> +
> +	iommu = iommu_alloc(iommu_mode);
>  
>  	container_path = iommu->mode->container_path;
>  	if (container_path) {
> @@ -453,10 +473,44 @@ struct iommu *iommu_init(const char *iommu_mode)
>  	return iommu;
>  }
>  
> +struct iommu *iommufd_iommu_init(int iommufd, u32 dev_id, u32 flags)
> +{
> +	struct iommu *iommu;
> +
> +	iommu = iommu_alloc("iommufd");

Use MODE_IOMMUFD instead of string literal.

> +
> +	iommu->iommufd = dup(iommufd);
> +	VFIO_ASSERT_GT(iommu->iommufd, 0);
> +
> +	iommu->ioas_id = iommufd_ioas_alloc(iommu->iommufd);

Please avoid duplicating this code. e.g. Something like this:

diff --git a/tools/testing/selftests/vfio/lib/iommu.c b/tools/testing/selftests/vfio/lib/iommu.c
index 644c049cf9f0..4909cda5c840 100644
--- a/tools/testing/selftests/vfio/lib/iommu.c
+++ b/tools/testing/selftests/vfio/lib/iommu.c
@@ -443,6 +443,19 @@ static struct iommu *iommu_alloc(const char *iommu_mode)
        return iommu;
 }

+static void iommufd_init(struct iommu *iommu, int iommufd)
+{
+       /*
+        * Require device->iommufd to be >0 so that a simple non-0 check can be
+        * used to check if iommufd is enabled. In practice open() will never
+        * return 0 unless stdin is closed.
+        */
+       VFIO_ASSERT_GT(iommufd, 0);
+
+       iommu->iommufd = iommufd;
+       iommu->ioas_id = iommufd_ioas_alloc(iommu->iommufd);
+}
+
 struct iommu *iommu_init(const char *iommu_mode)
 {
        const char *container_path;
@@ -459,15 +472,7 @@ struct iommu *iommu_init(const char *iommu_mode)
                version = ioctl(iommu->container_fd, VFIO_GET_API_VERSION);
                VFIO_ASSERT_EQ(version, VFIO_API_VERSION, "Unsupported version: %d\n", version);
        } else {
-               /*
-                * Require device->iommufd to be >0 so that a simple non-0 check can be
-                * used to check if iommufd is enabled. In practice open() will never
-                * return 0 unless stdin is closed.
-                */
-               iommu->iommufd = open("/dev/iommu", O_RDWR);
-               VFIO_ASSERT_GT(iommu->iommufd, 0);
-
-               iommu->ioas_id = iommufd_ioas_alloc(iommu->iommufd);
+               iommufd_init(iommu, open("/dev/iommu", O_RDWR));
        }

        return iommu;
@@ -478,11 +483,7 @@ struct iommu *iommufd_iommu_init(int iommufd, u32 dev_id, u32 flags)
        struct iommu *iommu;

        iommu = iommu_alloc("iommufd");
-
-       iommu->iommufd = dup(iommufd);
-       VFIO_ASSERT_GT(iommu->iommufd, 0);
-
-       iommu->ioas_id = iommufd_ioas_alloc(iommu->iommufd);
+       iommufd_init(iommu, dup(iommufd));

        if (flags & IOMMUFD_IOMMU_INIT_CREATE_PT)
                iommu->hwpt_id = iommufd_hwpt_alloc(iommu, dev_id);

> +
> +	if (flags & IOMMUFD_IOMMU_INIT_CREATE_PT)
> +		iommu->hwpt_id = iommufd_hwpt_alloc(iommu, dev_id);

Does this need to be part of iommufd_iommu_init()? Maybe it would be
better to expose a separate helper to allocate a HWPT for a given struct
iommu *.

This would enable use of HWPTs in iommus constructed by iommu_init() as
well, which someone may want to do in the future.

If you go this route, please introduce this in its own commit.

> +
> +	return iommu;
> +}
> +
> +static void iommufd_cleanup(struct iommu *iommu)
> +{
> +	struct iommu_destroy args = {
> +		.size = sizeof(args),
> +	};
> +
> +	if (iommu->hwpt_id) {
> +		args.id = iommu->hwpt_id;
> +		ioctl_assert(iommu->iommufd, IOMMU_DESTROY, &args);
> +	}
> +
> +	args.id = iommu->ioas_id;
> +	ioctl_assert(iommu->iommufd, IOMMU_DESTROY, &args);


Please create a helper function to do IOMMU_DESTROY ioctl. Then here you
can just do:

  if (iommu->hwpt_id)
          iommufd_iommu_destroy(iommu, iommu->hwpt_id);

  iommfd_iommu_destroy(iommu, iommu->ioas_id);

> +
> +	VFIO_ASSERT_EQ(close(iommu->iommufd), 0);
> +}
> +
>  void iommu_cleanup(struct iommu *iommu)
>  {
>  	if (iommu->iommufd)
> -		VFIO_ASSERT_EQ(close(iommu->iommufd), 0);
> +		iommufd_cleanup(iommu);
>  	else
>  		VFIO_ASSERT_EQ(close(iommu->container_fd), 0);
>  
> diff --git a/tools/testing/selftests/vfio/lib/vfio_pci_device.c b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> index fc75e04ef010..e2b71fe63cae 100644
> --- a/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> +++ b/tools/testing/selftests/vfio/lib/vfio_pci_device.c
> @@ -322,7 +322,7 @@ const char *vfio_pci_get_cdev_path(const char *bdf)
>  	return cdev_path;
>  }
>  
> -static void vfio_device_bind_iommufd(int device_fd, int iommufd)
> +static int vfio_device_bind_iommufd(int device_fd, int iommufd)
>  {
>  	struct vfio_device_bind_iommufd args = {
>  		.argsz = sizeof(args),
> @@ -330,6 +330,7 @@ static void vfio_device_bind_iommufd(int device_fd, int iommufd)
>  	};
>  
>  	ioctl_assert(device_fd, VFIO_DEVICE_BIND_IOMMUFD, &args);
> +	return args.out_devid;
>  }
>  
>  static void vfio_device_attach_iommufd_pt(int device_fd, u32 pt_id)
> @@ -342,6 +343,21 @@ static void vfio_device_attach_iommufd_pt(int device_fd, u32 pt_id)
>  	ioctl_assert(device_fd, VFIO_DEVICE_ATTACH_IOMMUFD_PT, &args);
>  }
>  
> +void vfio_pci_device_attach_iommu(struct vfio_pci_device *device, struct iommu *iommu)
> +{
> +	u32 pt_id = iommu->ioas_id;
> +
> +	/* Only iommufd supports changing struct iommu attachments */
> +	VFIO_ASSERT_TRUE(iommu->iommufd);
> +
> +	if (iommu->hwpt_id)
> +		pt_id = iommu->hwpt_id;

nit: This can be folded into the variable declaration.

  const u32 pt_id = iommu->hwpt_id ?: iommu->ioas_id;

> +
> +	VFIO_ASSERT_NE(pt_id, 0);

Why is this check needed?

> +	vfio_device_attach_iommufd_pt(device->fd, pt_id);
> +	device->iommu = iommu;
> +}

Please introduce vfio_pci_device_attach_iommu() in its own patch.

> +
>  static void vfio_pci_iommufd_setup(struct vfio_pci_device *device, const char *bdf)
>  {
>  	const char *cdev_path = vfio_pci_get_cdev_path(bdf);
> @@ -350,8 +366,8 @@ static void vfio_pci_iommufd_setup(struct vfio_pci_device *device, const char *b
>  	VFIO_ASSERT_GE(device->fd, 0);
>  	free((void *)cdev_path);
>  
> -	vfio_device_bind_iommufd(device->fd, device->iommu->iommufd);
> -	vfio_device_attach_iommufd_pt(device->fd, device->iommu->ioas_id);
> +	device->dev_id = vfio_device_bind_iommufd(device->fd, device->iommu->iommufd);
> +	vfio_pci_device_attach_iommu(device, device->iommu);
>  }
>  
>  struct vfio_pci_device *vfio_pci_device_init(const char *bdf, struct iommu *iommu)
> -- 
> 2.54.0.545.g6539524ca2-goog
>