Re: [PATCH v3 1/1] vfio: remove VFIO_GROUP_NOTIFY_SET_KVM
From: Tony Krowiak
Date: Fri May 20 2022 - 09:57:14 EST
On 5/19/22 2:33 PM, Matthew Rosato wrote:
Rather than relying on a notifier for associating the KVM with
the group, let's assume that the association has already been
made prior to device_open. The first time a device is opened
associate the group KVM with the device.
This fixes a user-triggerable oops in GVT.
Reviewed-by: Tony Krowiak <akrowiak@xxxxxxxxxxxxx>
Reviewed-by: Kevin Tian <kevin.tian@xxxxxxxxx>
Reviewed-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Jason Gunthorpe <jgg@xxxxxxxxxx>
Signed-off-by: Matthew Rosato <mjrosato@xxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/gvt/gtt.c | 4 +-
drivers/gpu/drm/i915/gvt/gvt.h | 3 -
drivers/gpu/drm/i915/gvt/kvmgt.c | 82 ++++++--------------------
drivers/s390/crypto/vfio_ap_ops.c | 35 ++---------
drivers/s390/crypto/vfio_ap_private.h | 3 -
drivers/vfio/vfio.c | 83 ++++++++++-----------------
include/linux/vfio.h | 6 +-
7 files changed, 57 insertions(+), 159 deletions(-)
diff --git a/drivers/s390/crypto/vfio_ap_ops.c b/drivers/s390/crypto/vfio_ap_ops.c
index e8914024f5b1..a7d2a95796d3 100644
--- a/drivers/s390/crypto/vfio_ap_ops.c
+++ b/drivers/s390/crypto/vfio_ap_ops.c
@@ -1284,25 +1284,6 @@ static void vfio_ap_mdev_unset_kvm(struct ap_matrix_mdev *matrix_mdev)
}
}
-static int vfio_ap_mdev_group_notifier(struct notifier_block *nb,
- unsigned long action, void *data)
-{
- int notify_rc = NOTIFY_OK;
- struct ap_matrix_mdev *matrix_mdev;
-
- if (action != VFIO_GROUP_NOTIFY_SET_KVM)
- return NOTIFY_OK;
-
- matrix_mdev = container_of(nb, struct ap_matrix_mdev, group_notifier);
-
- if (!data)
- vfio_ap_mdev_unset_kvm(matrix_mdev);
- else if (vfio_ap_mdev_set_kvm(matrix_mdev, data))
- notify_rc = NOTIFY_DONE;
-
- return notify_rc;
-}
-
static struct vfio_ap_queue *vfio_ap_find_queue(int apqn)
{
struct device *dev;
@@ -1402,11 +1383,10 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
unsigned long events;
int ret;
- matrix_mdev->group_notifier.notifier_call = vfio_ap_mdev_group_notifier;
- events = VFIO_GROUP_NOTIFY_SET_KVM;
+ if (!vdev->kvm)
+ return -EINVAL;
- ret = vfio_register_notifier(vdev, VFIO_GROUP_NOTIFY, &events,
- &matrix_mdev->group_notifier);
+ ret = vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm);
if (ret)
return ret;
I'm sorry I didn't see this with my last review, but maybe move the call
to vfio_ap_mdev_set_kvm(matrix_mdev, vdev->kvm) after the successful
registration of the IOMMU notifier? This way you won't be plugging AP queues
into the guest only to remove them if the registration fails.
@@ -1415,12 +1395,11 @@ static int vfio_ap_mdev_open_device(struct vfio_device *vdev)
ret = vfio_register_notifier(vdev, VFIO_IOMMU_NOTIFY, &events,
&matrix_mdev->iommu_notifier);
if (ret)
- goto out_unregister_group;
+ goto err_kvm;
return 0;
-out_unregister_group:
- vfio_unregister_notifier(vdev, VFIO_GROUP_NOTIFY,
- &matrix_mdev->group_notifier);
+err_kvm:
+ vfio_ap_mdev_unset_kvm(matrix_mdev);
return ret;
}
@@ -1431,8 +1410,6 @@ static void vfio_ap_mdev_close_device(struct vfio_device *vdev)
vfio_unregister_notifier(vdev, VFIO_IOMMU_NOTIFY,
&matrix_mdev->iommu_notifier);
- vfio_unregister_notifier(vdev, VFIO_GROUP_NOTIFY,
- &matrix_mdev->group_notifier);
vfio_ap_mdev_unset_kvm(matrix_mdev);
}
diff --git a/drivers/s390/crypto/vfio_ap_private.h b/drivers/s390/crypto/vfio_ap_private.h
index 648fcaf8104a..a26efd804d0d 100644
--- a/drivers/s390/crypto/vfio_ap_private.h
+++ b/drivers/s390/crypto/vfio_ap_private.h
@@ -81,8 +81,6 @@ struct ap_matrix {
* @node: allows the ap_matrix_mdev struct to be added to a list
* @matrix: the adapters, usage domains and control domains assigned to the
* mediated matrix device.
- * @group_notifier: notifier block used for specifying callback function for
- * handling the VFIO_GROUP_NOTIFY_SET_KVM event
* @iommu_notifier: notifier block used for specifying callback function for
* handling the VFIO_IOMMU_NOTIFY_DMA_UNMAP even
* @kvm: the struct holding guest's state
@@ -94,7 +92,6 @@ struct ap_matrix_mdev {
struct vfio_device vdev;
struct list_head node;
struct ap_matrix matrix;
- struct notifier_block group_notifier;
struct notifier_block iommu_notifier;
struct kvm *kvm;
crypto_hook pqap_hook;
diff --git a/drivers/vfio/vfio.c b/drivers/vfio/vfio.c
index cfcff7764403..831fc722e3f8 100644
--- a/drivers/vfio/vfio.c
+++ b/drivers/vfio/vfio.c
@@ -1083,10 +1083,21 @@ static struct file *vfio_device_open(struct vfio_device *device)
mutex_lock(&device->dev_set->lock);
device->open_count++;
- if (device->open_count == 1 && device->ops->open_device) {
- ret = device->ops->open_device(device);
- if (ret)
- goto err_undo_count;
+ if (device->open_count == 1) {
+ /*
+ * Here we pass the KVM pointer with the group under the read
+ * lock. If the device driver will use it, it must obtain a
+ * reference and release it during close_device.
+ */
+ down_read(&device->group->group_rwsem);
+ device->kvm = device->group->kvm;
+
+ if (device->ops->open_device) {
+ ret = device->ops->open_device(device);
+ if (ret)
+ goto err_undo_count;
+ }
+ up_read(&device->group->group_rwsem);
}
mutex_unlock(&device->dev_set->lock);
@@ -1119,10 +1130,14 @@ static struct file *vfio_device_open(struct vfio_device *device)
err_close_device:
mutex_lock(&device->dev_set->lock);
+ down_read(&device->group->group_rwsem);
if (device->open_count == 1 && device->ops->close_device)
device->ops->close_device(device);
err_undo_count:
device->open_count--;
+ if (device->open_count == 0 && device->kvm)
+ device->kvm = NULL;
+ up_read(&device->group->group_rwsem);
mutex_unlock(&device->dev_set->lock);
module_put(device->dev->driver->owner);
err_unassign_container:
@@ -1315,9 +1330,13 @@ static int vfio_device_fops_release(struct inode *inode, struct file *filep)
mutex_lock(&device->dev_set->lock);
vfio_assert_device_open(device);
+ down_read(&device->group->group_rwsem);
if (device->open_count == 1 && device->ops->close_device)
device->ops->close_device(device);
+ up_read(&device->group->group_rwsem);
device->open_count--;
+ if (device->open_count == 0)
+ device->kvm = NULL;
mutex_unlock(&device->dev_set->lock);
module_put(device->dev->driver->owner);
@@ -1726,8 +1745,8 @@ EXPORT_SYMBOL_GPL(vfio_file_enforced_coherent);
* @file: VFIO group file
* @kvm: KVM to link
*
- * The kvm pointer will be forwarded to all the vfio_device's attached to the
- * VFIO file via the VFIO_GROUP_NOTIFY_SET_KVM notifier.
+ * When a VFIO device is first opened the KVM will be available in
+ * device->kvm if one was associated with the group.
*/
void vfio_file_set_kvm(struct file *file, struct kvm *kvm)
{
@@ -1738,8 +1757,6 @@ void vfio_file_set_kvm(struct file *file, struct kvm *kvm)
down_write(&group->group_rwsem);
group->kvm = kvm;
- blocking_notifier_call_chain(&group->notifier,
- VFIO_GROUP_NOTIFY_SET_KVM, kvm);
up_write(&group->group_rwsem);
}
EXPORT_SYMBOL_GPL(vfio_file_set_kvm);
@@ -2006,7 +2023,8 @@ static int vfio_register_iommu_notifier(struct vfio_group *group,
struct vfio_iommu_driver *driver;
int ret;
- down_read(&group->group_rwsem);
+ lockdep_assert_held_read(&group->group_rwsem);
+
container = group->container;
driver = container->iommu_driver;
if (likely(driver && driver->ops->register_notifier))
@@ -2014,7 +2032,6 @@ static int vfio_register_iommu_notifier(struct vfio_group *group,
events, nb);
else
ret = -ENOTTY;
- up_read(&group->group_rwsem);
return ret;
}
@@ -2026,7 +2043,8 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
struct vfio_iommu_driver *driver;
int ret;
- down_read(&group->group_rwsem);
+ lockdep_assert_held_read(&group->group_rwsem);
+
container = group->container;
driver = container->iommu_driver;
if (likely(driver && driver->ops->unregister_notifier))
@@ -2034,47 +2052,10 @@ static int vfio_unregister_iommu_notifier(struct vfio_group *group,
nb);
else
ret = -ENOTTY;
- up_read(&group->group_rwsem);
return ret;
}
-static int vfio_register_group_notifier(struct vfio_group *group,
- unsigned long *events,
- struct notifier_block *nb)
-{
- int ret;
- bool set_kvm = false;
-
- if (*events & VFIO_GROUP_NOTIFY_SET_KVM)
- set_kvm = true;
-
- /* clear known events */
- *events &= ~VFIO_GROUP_NOTIFY_SET_KVM;
-
- /* refuse to continue if still events remaining */
- if (*events)
- return -EINVAL;
-
- ret = blocking_notifier_chain_register(&group->notifier, nb);
- if (ret)
- return ret;
-
- /*
- * The attaching of kvm and vfio_group might already happen, so
- * here we replay once upon registration.
- */
- if (set_kvm) {
- down_read(&group->group_rwsem);
- if (group->kvm)
- blocking_notifier_call_chain(&group->notifier,
- VFIO_GROUP_NOTIFY_SET_KVM,
- group->kvm);
- up_read(&group->group_rwsem);
- }
- return 0;
-}
-
int vfio_register_notifier(struct vfio_device *device,
enum vfio_notify_type type, unsigned long *events,
struct notifier_block *nb)
@@ -2090,9 +2071,6 @@ int vfio_register_notifier(struct vfio_device *device,
case VFIO_IOMMU_NOTIFY:
ret = vfio_register_iommu_notifier(group, events, nb);
break;
- case VFIO_GROUP_NOTIFY:
- ret = vfio_register_group_notifier(group, events, nb);
- break;
default:
ret = -EINVAL;
}
@@ -2114,9 +2092,6 @@ int vfio_unregister_notifier(struct vfio_device *device,
case VFIO_IOMMU_NOTIFY:
ret = vfio_unregister_iommu_notifier(group, nb);
break;
- case VFIO_GROUP_NOTIFY:
- ret = blocking_notifier_chain_unregister(&group->notifier, nb);
- break;
default:
ret = -EINVAL;
}
diff --git a/include/linux/vfio.h b/include/linux/vfio.h
index 45b287826ce6..aa888cc51757 100644
--- a/include/linux/vfio.h
+++ b/include/linux/vfio.h
@@ -36,6 +36,8 @@ struct vfio_device {
struct vfio_device_set *dev_set;
struct list_head dev_set_list;
unsigned int migration_flags;
+ /* Driver must reference the kvm during open_device or never touch it */
+ struct kvm *kvm;
/* Members below here are private, not for driver use */
refcount_t refcount;
@@ -155,15 +157,11 @@ extern int vfio_dma_rw(struct vfio_device *device, dma_addr_t user_iova,
/* each type has independent events */
enum vfio_notify_type {
VFIO_IOMMU_NOTIFY = 0,
- VFIO_GROUP_NOTIFY = 1,
};
/* events for VFIO_IOMMU_NOTIFY */
#define VFIO_IOMMU_NOTIFY_DMA_UNMAP BIT(0)
-/* events for VFIO_GROUP_NOTIFY */
-#define VFIO_GROUP_NOTIFY_SET_KVM BIT(0)
-
extern int vfio_register_notifier(struct vfio_device *device,
enum vfio_notify_type type,
unsigned long *required_events,