Re: [PATCH V2 06/11] vfio: Introduce and set noiommu flag on vfio_device

Mostafa Saleh
2026-03-22T10:02:13Z

On Thu, Mar 12, 2026 at 08:56:32AM -0700, Jacob Pan wrote:
> When a VFIO device is added to a noiommu group, set the noiommu flag on
> the vfio_device structure to indicate that the device operates in
> noiommu mode.
>
> Also update function signatures to pass vfio_device instead of device,
> which has the direct access to the noiommu flag.
>
> Signed-off-by: Jacob Pan <jacob.pan@linux.microsoft.com>

Reviewed-by: Mostafa Saleh <smostafa@google.com>

Thanks,
Mostafa

> ---
> drivers/vfio/group.c | 21 +++++++++++----------
> include/linux/vfio.h | 1 +
> 2 files changed, 12 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/vfio/group.c b/drivers/vfio/group.c
> index 98f2a4f2ebff..6f98c57de9e0 100644
> --- a/drivers/vfio/group.c
> +++ b/drivers/vfio/group.c
> @@ -588,7 +588,7 @@ static struct vfio_group *vfio_create_group(struct iommu_group *iommu_group,
> return ret;
> }
>
> -static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev,
> +static struct vfio_group *vfio_noiommu_group_alloc(struct vfio_device *vdev,
> enum vfio_group_type type)
> {
> struct iommu_group *iommu_group;
> @@ -610,7 +610,7 @@ static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev,
> ret = iommu_group_set_name(iommu_group, "vfio-noiommu");
> if (ret)
> goto out_put_group;
> - ret = iommu_group_add_device(iommu_group, dev);
> + ret = iommu_group_add_device(iommu_group, vdev->dev);
> if (ret)
> goto out_put_group;
>
> @@ -625,7 +625,7 @@ static struct vfio_group *vfio_noiommu_group_alloc(struct device *dev,
> return group;
>
> out_remove_device:
> - iommu_group_remove_device(dev);
> + iommu_group_remove_device(vdev->dev);
> out_put_group:
> iommu_group_put(iommu_group);
> return ERR_PTR(ret);
> @@ -646,23 +646,24 @@ static bool vfio_group_has_device(struct vfio_group *group, struct device *dev)
> return false;
> }
>
> -static struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
> +static struct vfio_group *vfio_group_find_or_alloc(struct vfio_device *vdev)
> {
> struct iommu_group *iommu_group;
> struct vfio_group *group;
>
> - iommu_group = iommu_group_get(dev);
> + iommu_group = iommu_group_get(vdev->dev);
> if (!iommu_group && vfio_noiommu) {
> + vdev->noiommu = 1;
> /*
> * With noiommu enabled, create an IOMMU group for devices that
> * don't already have one, implying no IOMMU hardware/driver
> * exists. Taint the kernel because we're about to give a DMA
> * capable device to a user without IOMMU protection.
> */
> - group = vfio_noiommu_group_alloc(dev, VFIO_NO_IOMMU);
> + group = vfio_noiommu_group_alloc(vdev, VFIO_NO_IOMMU);
> if (!IS_ERR(group)) {
> add_taint(TAINT_USER, LOCKDEP_STILL_OK);
> - dev_warn(dev, "Adding kernel taint for vfio-noiommu group on device\n");
> + dev_warn(vdev->dev, "Adding kernel taint for vfio-noiommu group on device\n");
> }
> return group;
> }
> @@ -673,7 +674,7 @@ static struct vfio_group *vfio_group_find_or_alloc(struct device *dev)
> mutex_lock(&vfio.group_lock);
> group = vfio_group_find_from_iommu(iommu_group);
> if (group) {
> - if (WARN_ON(vfio_group_has_device(group, dev)))
> + if (WARN_ON(vfio_group_has_device(group, vdev->dev)))
> group = ERR_PTR(-EINVAL);
> else
> refcount_inc(&group->drivers);
> @@ -693,9 +694,9 @@ int vfio_device_set_group(struct vfio_device *device,
> struct vfio_group *group;
>
> if (type == VFIO_IOMMU)
> - group = vfio_group_find_or_alloc(device->dev);
> + group = vfio_group_find_or_alloc(device);
> else
> - group = vfio_noiommu_group_alloc(device->dev, type);
> + group = vfio_noiommu_group_alloc(device, type);
>
> if (IS_ERR(group))
> return PTR_ERR(group);
> diff --git a/include/linux/vfio.h b/include/linux/vfio.h
> index e90859956514..844d14839f96 100644
> --- a/include/linux/vfio.h
> +++ b/include/linux/vfio.h
> @@ -72,6 +72,7 @@ struct vfio_device {
> u8 iommufd_attached:1;
> #endif
> u8 cdev_opened:1;
> + u8 noiommu:1;
> #ifdef CONFIG_DEBUG_FS
> /*
> * debug_root is a static property of the vfio_device
> --
> 2.34.1
>