[PATCH 4.9 19/61] drm/virtio: fix vq wait_event condition

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

--

From: Gerd Hoffmann 

commit d02d270014f70dcab0117776b81a37b6fca745ae upstream.

Wait until we have enough space in the virt queue to actually queue up
our request.  Avoids the guest spinning in case we have a non-zero
amount of free entries but not enough for the request.

Cc: sta...@vger.kernel.org
Reported-by: Alain Magloire 
Signed-off-by: Gerd Hoffmann 
Reviewed-by: Dave Airlie 
Link: 
http://patchwork.freedesktop.org/patch/msgid/20180403095904.11152-1-kra...@redhat.com
Signed-off-by: Sean Paul 
Signed-off-by: Greg Kroah-Hartman 

---
 drivers/gpu/drm/virtio/virtgpu_vq.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -324,7 +324,7 @@ retry:
ret = virtqueue_add_sgs(vq, sgs, outcnt, incnt, vbuf, GFP_ATOMIC);
if (ret == -ENOSPC) {
spin_unlock(>ctrlq.qlock);
-   wait_event(vgdev->ctrlq.ack_queue, vq->num_free);
+   wait_event(vgdev->ctrlq.ack_queue, vq->num_free >= outcnt + 
incnt);
spin_lock(>ctrlq.qlock);
goto retry;
} else {
@@ -399,7 +399,7 @@ retry:
ret = virtqueue_add_sgs(vq, sgs, outcnt, 0, vbuf, GFP_ATOMIC);
if (ret == -ENOSPC) {
spin_unlock(>cursorq.qlock);
-   wait_event(vgdev->cursorq.ack_queue, vq->num_free);
+   wait_event(vgdev->cursorq.ack_queue, vq->num_free >= outcnt);
spin_lock(>cursorq.qlock);
goto retry;
} else {

[PATCH 4.9 19/61] drm/virtio: fix vq wait_event condition

[Greg Kroah-Hartman]

4.9-stable review patch.  If anyone has any objections, please let me know.

--

From: Gerd Hoffmann 

commit d02d270014f70dcab0117776b81a37b6fca745ae upstream.

Wait until we have enough space in the virt queue to actually queue up
our request.  Avoids the guest spinning in case we have a non-zero
amount of free entries but not enough for the request.

Cc: sta...@vger.kernel.org
Reported-by: Alain Magloire 
Signed-off-by: Gerd Hoffmann 
Reviewed-by: Dave Airlie 
Link: 
http://patchwork.freedesktop.org/patch/msgid/20180403095904.11152-1-kra...@redhat.com
Signed-off-by: Sean Paul 
Signed-off-by: Greg Kroah-Hartman 

---
 drivers/gpu/drm/virtio/virtgpu_vq.c |4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/drivers/gpu/drm/virtio/virtgpu_vq.c
+++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
@@ -324,7 +324,7 @@ retry:
ret = virtqueue_add_sgs(vq, sgs, outcnt, incnt, vbuf, GFP_ATOMIC);
if (ret == -ENOSPC) {
spin_unlock(>ctrlq.qlock);
-   wait_event(vgdev->ctrlq.ack_queue, vq->num_free);
+   wait_event(vgdev->ctrlq.ack_queue, vq->num_free >= outcnt + 
incnt);
spin_lock(>ctrlq.qlock);
goto retry;
} else {
@@ -399,7 +399,7 @@ retry:
ret = virtqueue_add_sgs(vq, sgs, outcnt, 0, vbuf, GFP_ATOMIC);
if (ret == -ENOSPC) {
spin_unlock(>cursorq.qlock);
-   wait_event(vgdev->cursorq.ack_queue, vq->num_free);
+   wait_event(vgdev->cursorq.ack_queue, vq->num_free >= outcnt);
spin_lock(>cursorq.qlock);
goto retry;
} else {