From d02d270014f70dcab0117776b81a37b6fca745ae Mon Sep 17 00:00:00 2001
From: Gerd Hoffmann <kraxel@redhat.com>
Date: Tue, 3 Apr 2018 11:59:04 +0200
Subject: [PATCH] drm/virtio: fix vq wait_event condition
Git-commit: d02d270014f70dcab0117776b81a37b6fca745ae
Patch-mainline: v4.17-rc3
References: bsc#1051510
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: stable@vger.kernel.org
Reported-by: Alain Magloire <amagloire@blackberry.com>
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Reviewed-by: Dave Airlie <airlied@redhat.com>
Link: http://patchwork.freedesktop.org/patch/msgid/20180403095904.11152-1-kraxel@redhat.com
Signed-off-by: Sean Paul <seanpaul@chromium.org>
Acked-by: Takashi Iwai <tiwai@suse.de>
---
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
@@ -293,7 +293,7 @@ retry:
ret = virtqueue_add_sgs(vq, sgs, outcnt, incnt, vbuf, GFP_ATOMIC);
if (ret == -ENOSPC) {
spin_unlock(&vgdev->ctrlq.qlock);
- wait_event(vgdev->ctrlq.ack_queue, vq->num_free);
+ wait_event(vgdev->ctrlq.ack_queue, vq->num_free >= outcnt + incnt);
spin_lock(&vgdev->ctrlq.qlock);
goto retry;
} else {
@@ -368,7 +368,7 @@ retry:
ret = virtqueue_add_sgs(vq, sgs, outcnt, 0, vbuf, GFP_ATOMIC);
if (ret == -ENOSPC) {
spin_unlock(&vgdev->cursorq.qlock);
- wait_event(vgdev->cursorq.ack_queue, vq->num_free);
+ wait_event(vgdev->cursorq.ack_queue, vq->num_free >= outcnt);
spin_lock(&vgdev->cursorq.qlock);
goto retry;
} else {