On Fri, 29 Apr 2022 15:46:17 -0300
Jason Gunthorpe <jgg@xxxxxxxxxx> wrote:
> Now that the iommu core takes care of isolation there is no race between
> driver attach and container unset. Once iommu_group_release_dma_owner()
> returns the device can immediately be re-used.
>
> Remove this mechanism.
>
> Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
> ---
> drivers/vfio/vfio.c | 20 --------------------
> 1 file changed, 20 deletions(-)
>
> This was missed in Baolu's series, and applies on top of "iommu: Remove iommu
> group changes notifier"
>
> diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
> index 0c766384cee0f8..4a1847f50c9289 100644
> --- a/drivers/vfio/vfio.c
> +++ b/drivers/vfio/vfio.c
> @@ -74,7 +74,6 @@ struct vfio_group {
> struct list_head vfio_next;
> struct list_head container_next;
> atomic_t opened;
> - wait_queue_head_t container_q;
> enum vfio_group_type type;
> unsigned int dev_counter;
> struct kvm *kvm;
> @@ -363,7 +362,6 @@ static struct vfio_group *vfio_group_alloc(struct iommu_group *iommu_group,
> refcount_set(&group->users, 1);
> INIT_LIST_HEAD(&group->device_list);
> mutex_init(&group->device_lock);
> - init_waitqueue_head(&group->container_q);
> group->iommu_group = iommu_group;
> /* put in vfio_group_release() */
> iommu_group_ref_get(iommu_group);
> @@ -723,23 +721,6 @@ void vfio_unregister_group_dev(struct vfio_device *device)
> group->dev_counter--;
> mutex_unlock(&group->device_lock);
>
> - /*
> - * In order to support multiple devices per group, devices can be
> - * plucked from the group while other devices in the group are still
> - * in use. The container persists with this group and those remaining
> - * devices still attached. If the user creates an isolation violation
> - * by binding this device to another driver while the group is still in
> - * use, that's their fault. However, in the case of removing the last,
> - * or potentially the only, device in the group there can be no other
> - * in-use devices in the group. The user has done their due diligence
> - * and we should lay no claims to those devices. In order to do that,
> - * we need to make sure the group is detached from the container.
> - * Without this stall, we're potentially racing with a user process
> - * that may attempt to immediately bind this device to another driver.
> - */
> - if (list_empty(&group->device_list))
> - wait_event(group->container_q, !group->container);
> -
> if (group->type == VFIO_NO_IOMMU || group->type == VFIO_EMULATED_IOMMU)
> iommu_group_remove_device(device->dev);
>
> @@ -984,7 +965,6 @@ static void __vfio_group_unset_container(struct vfio_group *group)
> iommu_group_release_dma_owner(group->iommu_group);
>
> group->container = NULL;
> - wake_up(&group->container_q);
> list_del(&group->container_next);
>
> /* Detaching the last group deprivileges a container, remove iommu */
>
> base-commit: 46788c84354d07f8b1e5df87e805500611fd04fb
Applied to vfio next branch for v5.19. Thanks,
Alex
