Re: [PATCH] drm/virtio: fix vq wait_event condition

[Dave Airlie]

On 20 April 2018 at 17:22, Gerd Hoffmann <kraxel@xxxxxxxxxx> wrote:
> On Tue, Apr 03, 2018 at 11:59:04AM +0200, Gerd Hoffmann wrote:
>> 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.
>
> Ping airlied, can you please either pick it up or review so I can commit
> myself?

Just in case it got lost from my phone,

Reviewed-by: Dave Airlie <airlied@xxxxxxxxxx>

>
> thanks,
>   Gerd
>
>> Cc: stable@xxxxxxxxxxxxxxx
>> Reported-by: Alain Magloire <amagloire@xxxxxxxxxxxxxx>
>> Signed-off-by: Gerd Hoffmann <kraxel@xxxxxxxxxx>
>> ---
>>  drivers/gpu/drm/virtio/virtgpu_vq.c | 4 ++--
>>  1 file changed, 2 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/virtio/virtgpu_vq.c b/drivers/gpu/drm/virtio/virtgpu_vq.c
>> index 48e4f1df6e..020070d483 100644
>> --- a/drivers/gpu/drm/virtio/virtgpu_vq.c
>> +++ b/drivers/gpu/drm/virtio/virtgpu_vq.c
>> @@ -293,7 +293,7 @@ static int virtio_gpu_queue_ctrl_buffer_locked(struct virtio_gpu_device *vgdev,
>>       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 @@ static int virtio_gpu_queue_cursor(struct virtio_gpu_device *vgdev,
>>       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 {
>> --
>> 2.9.3
>>
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