vfio: Delete container_q

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@nvidia.com>
Reviewed-by: Kevin Tian <kevin.tian@intel.com>
Link: https://lore.kernel.org/r/0-v1-a1e8791d795b+6b-vfio_container_q_jgg@nvidia.com
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>

diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index cc0d337..8cb7ba0 100644 (file)
--- 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);
@@ -684,23 +682,6 @@ 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);
 
@@ -945,7 +926,6 @@ 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 */