2023-02-03 23:34:18

by Ryan Neph

Subject: [PATCH v2] drm/virtio: exbuf->fence_fd unmodified on interrupted wait

An interrupted dma_fence_wait() becomes an -ERESTARTSYS returned
to userspace ioctl(DRM_IOCTL_VIRTGPU_EXECBUFFER) calls, prompting to
retry the ioctl(), but the passed exbuf->fence_fd has been reset to -1,
making the retry attempt fail at sync_file_get_fence().

The uapi for DRM_IOCTL_VIRTGPU_EXECBUFFER is changed to retain the
passed value for exbuf->fence_fd when returning anything besides a
successful result from the ioctl.

Fixes: 2cd7b6f08bc4 ("drm/virtio: add in/out fence support for explicit synchronization")
Signed-off-by: Ryan Neph <[email protected]>
Reviewed-by: Rob Clark <[email protected]>
Reviewed-by: Dmitry Osipenko <[email protected]>

---

Changes in v2:
- No longer modifies exbuf->fence_fd unless DRM_IOCTL_VIRTGPU_EXECBUFFER
succeeds.
- Added r-b tags (Rob/Dmitry) from v1.

drivers/gpu/drm/virtio/virtgpu_ioctl.c | 5 +----
include/uapi/drm/virtgpu_drm.h | 1 +
2 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index 9f4a90493aea..da45215a933d 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -126,7 +126,6 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
void __user *user_bo_handles = NULL;
struct virtio_gpu_object_array *buflist = NULL;
struct sync_file *sync_file;
- int in_fence_fd = exbuf->fence_fd;
int out_fence_fd = -1;
void *buf;
uint64_t fence_ctx;
@@ -152,13 +151,11 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
ring_idx = exbuf->ring_idx;
}

- exbuf->fence_fd = -1;
-
virtio_gpu_create_context(dev, file);
if (exbuf->flags & VIRTGPU_EXECBUF_FENCE_FD_IN) {
struct dma_fence *in_fence;

- in_fence = sync_file_get_fence(in_fence_fd);
+ in_fence = sync_file_get_fence(exbuf->fence_fd);

if (!in_fence)
return -EINVAL;
diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
index 0512fde5e697..7b158fcb02b4 100644
--- a/include/uapi/drm/virtgpu_drm.h
+++ b/include/uapi/drm/virtgpu_drm.h
@@ -64,6 +64,7 @@ struct drm_virtgpu_map {
__u32 pad;
};

+/* fence_fd is modified on success if VIRTGPU_EXECBUF_FENCE_FD_OUT flag is set. */
struct drm_virtgpu_execbuffer {
__u32 flags;
__u32 size;
--
2.39.1.519.gcb327c4b5f-goog

2023-02-06 17:20:57

by Dmitry Osipenko

Subject: Re: [PATCH v2] drm/virtio: exbuf->fence_fd unmodified on interrupted wait

On 2/4/23 02:33, Ryan Neph wrote:
> An interrupted dma_fence_wait() becomes an -ERESTARTSYS returned
> to userspace ioctl(DRM_IOCTL_VIRTGPU_EXECBUFFER) calls, prompting to
> retry the ioctl(), but the passed exbuf->fence_fd has been reset to -1,
> making the retry attempt fail at sync_file_get_fence().
>
> The uapi for DRM_IOCTL_VIRTGPU_EXECBUFFER is changed to retain the
> passed value for exbuf->fence_fd when returning anything besides a
> successful result from the ioctl.
>
> Fixes: 2cd7b6f08bc4 ("drm/virtio: add in/out fence support for explicit synchronization")
> Signed-off-by: Ryan Neph <[email protected]>
> Reviewed-by: Rob Clark <[email protected]>
> Reviewed-by: Dmitry Osipenko <[email protected]>
>
> ---
>
> Changes in v2:
> - No longer modifies exbuf->fence_fd unless DRM_IOCTL_VIRTGPU_EXECBUFFER
> succeeds.
> - Added r-b tags (Rob/Dmitry) from v1.

Thanks! Applied to misc-fixes

--
Best regards,
Dmitry