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Subject[PATCH 2/5] drm/virtio: add uapi for in and out explicit fences
Date
Add a new field called fence_fd that will be used by userspace to send
in-fences to the kernel and receive out-fences created by the kernel.

This uapi enables virtio to take advantage of explicit synchronization of
dma-bufs.

There are two new flags:

* VIRTGPU_EXECBUF_FENCE_FD_IN to be used when passing an in-fence fd.
* VIRTGPU_EXECBUF_FENCE_FD_OUT to be used when requesting an out-fence fd

The execbuffer IOCTL is now read-write to allow the userspace to read the
out-fence.

On error -1 should be returned in the fence_fd field.

Signed-off-by: Gustavo Padovan <gustavo.padovan@collabora.com>
Signed-off-by: Robert Foss <robert.foss@collabora.com>
---
Changes since v2:
- Since exbuf-flags is a new flag, check that unsupported
flags aren't set.

drivers/gpu/drm/virtio/virtgpu_ioctl.c | 5 +++++
include/uapi/drm/virtgpu_drm.h | 13 ++++++++++---
2 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_ioctl.c b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
index d01a9ed100d1..1af289b28fc4 100644
--- a/drivers/gpu/drm/virtio/virtgpu_ioctl.c
+++ b/drivers/gpu/drm/virtio/virtgpu_ioctl.c
@@ -116,9 +116,14 @@ static int virtio_gpu_execbuffer_ioctl(struct drm_device *dev, void *data,
struct ww_acquire_ctx ticket;
void *buf;

+ exbuf->fence_fd = -1;
+
if (vgdev->has_virgl_3d == false)
return -ENOSYS;

+ if ((exbuf->flags & ~VIRTGPU_EXECBUF_FLAGS))
+ return -EINVAL;
+
INIT_LIST_HEAD(&validate_list);
if (exbuf->num_bo_handles) {

diff --git a/include/uapi/drm/virtgpu_drm.h b/include/uapi/drm/virtgpu_drm.h
index 9a781f0611df..91062f4ac7c5 100644
--- a/include/uapi/drm/virtgpu_drm.h
+++ b/include/uapi/drm/virtgpu_drm.h
@@ -47,6 +47,13 @@ extern "C" {
#define DRM_VIRTGPU_WAIT 0x08
#define DRM_VIRTGPU_GET_CAPS 0x09

+#define VIRTGPU_EXECBUF_FENCE_FD_IN 0x01
+#define VIRTGPU_EXECBUF_FENCE_FD_OUT 0x02
+#define VIRTGPU_EXECBUF_FLAGS (\
+ VIRTGPU_EXECBUF_FENCE_FD_IN |\
+ VIRTGPU_EXECBUF_FENCE_FD_OUT |\
+ 0)
+
struct drm_virtgpu_map {
__u64 offset; /* use for mmap system call */
__u32 handle;
@@ -54,12 +61,12 @@ struct drm_virtgpu_map {
};

struct drm_virtgpu_execbuffer {
- __u32 flags; /* for future use */
+ __u32 flags;
__u32 size;
__u64 command; /* void* */
__u64 bo_handles;
__u32 num_bo_handles;
- __u32 pad;
+ __s32 fence_fd;
};

#define VIRTGPU_PARAM_3D_FEATURES 1 /* do we have 3D features in the hw */
@@ -137,7 +144,7 @@ struct drm_virtgpu_get_caps {
DRM_IOWR(DRM_COMMAND_BASE + DRM_VIRTGPU_MAP, struct drm_virtgpu_map)

#define DRM_IOCTL_VIRTGPU_EXECBUFFER \
- DRM_IOW(DRM_COMMAND_BASE + DRM_VIRTGPU_EXECBUFFER,\
+ DRM_IOWR(DRM_COMMAND_BASE + DRM_VIRTGPU_EXECBUFFER,\
struct drm_virtgpu_execbuffer)

#define DRM_IOCTL_VIRTGPU_GETPARAM \
--
2.17.1
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