venus: add vn_renderer_bo_export_sync_file helper

...and a renderer internal helper shared by virtgpu and vtest backend
when supported.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/39401>

src/virtio/vulkan/vn_renderer.h

@@ -165,6 +165,9 @@ struct vn_renderer_bo_ops {
    int (*export_dma_buf)(struct vn_renderer *renderer,
                          struct vn_renderer_bo *bo);
 
+   int (*export_sync_file)(struct vn_renderer *renderer,
+                           struct vn_renderer_bo *bo);
+
    /* map is not thread-safe */
    void *(*map)(struct vn_renderer *renderer,
                 struct vn_renderer_bo *bo,
@@ -375,6 +378,13 @@ vn_renderer_bo_export_dma_buf(struct vn_renderer *renderer,
    return renderer->bo_ops.export_dma_buf(renderer, bo);
 }
 
+static inline int
+vn_renderer_bo_export_sync_file(struct vn_renderer *renderer,
+                                struct vn_renderer_bo *bo)
+{
+   return renderer->bo_ops.export_sync_file(renderer, bo);
+}
+
 static inline void *
 vn_renderer_bo_map(struct vn_renderer *renderer,
                    struct vn_renderer_bo *bo,

src/virtio/vulkan/vn_renderer_internal.c

@@ -5,6 +5,12 @@
 
 #include "vn_renderer_internal.h"
 
+#ifdef HAVE_LIBDRM
+#include <xf86drm.h>
+
+#include "drm-uapi/dma-buf.h"
+#endif
+
 /* 3 seconds */
 #define VN_RENDERER_SHMEM_CACHE_EXPIRACY (3ll * 1000 * 1000)
 
@@ -180,3 +186,40 @@ vn_renderer_shmem_cache_get(struct vn_renderer_shmem_cache *cache,
 
    return shmem;
 }
+
+int
+vn_renderer_bo_export_sync_file_internal(struct vn_renderer *renderer,
+                                         struct vn_renderer_bo *bo)
+{
+#ifdef HAVE_LIBDRM
+   /* Don't keep trying an IOCTL that doesn't exist. */
+   static bool no_dma_buf_sync_file = false;
+   if (no_dma_buf_sync_file)
+      return -1;
+
+   /* For simplicity, export dma-buf here and rely on the dma-buf sync file
+    * export api. On legacy kernels without the new uapi, for virtgpu backend,
+    * we do have the fallback option of doing DRM_IOCTL_VIRTGPU_WAIT instead.
+    */
+   int dma_buf_fd = vn_renderer_bo_export_dma_buf(renderer, bo);
+   if (dma_buf_fd < 0)
+      return -1;
+
+   struct dma_buf_export_sync_file export = {
+      .flags = DMA_BUF_SYNC_RW,
+      .fd = -1,
+   };
+   int ret = drmIoctl(dma_buf_fd, DMA_BUF_IOCTL_EXPORT_SYNC_FILE, &export);
+
+   close(dma_buf_fd);
+
+   if (ret && (errno == ENOTTY || errno == EBADF || errno == ENOSYS)) {
+      no_dma_buf_sync_file = true;
+      return -1;
+   }
+
+   return export.fd;
+#else  /* HAVE_LIBDRM */
+   return -1;
+#endif /* HAVE_LIBDRM */
+}

src/virtio/vulkan/vn_renderer_internal.h

@@ -51,4 +51,8 @@ struct vn_renderer_shmem *
 vn_renderer_shmem_cache_get(struct vn_renderer_shmem_cache *cache,
                             size_t size);
 
+int
+vn_renderer_bo_export_sync_file_internal(struct vn_renderer *renderer,
+                                         struct vn_renderer_bo *bo);
+
 #endif /* VN_RENDERER_INTERNAL_H */

src/virtio/vulkan/vn_renderer_virtgpu.c

@@ -1796,6 +1796,8 @@ virtgpu_init(struct virtgpu *gpu)
    gpu->base.bo_ops.create_from_dma_buf = virtgpu_bo_create_from_dma_buf;
    gpu->base.bo_ops.destroy = virtgpu_bo_destroy;
    gpu->base.bo_ops.export_dma_buf = virtgpu_bo_export_dma_buf;
+   gpu->base.bo_ops.export_sync_file =
+      vn_renderer_bo_export_sync_file_internal;
    gpu->base.bo_ops.map = virtgpu_bo_map;
    gpu->base.bo_ops.flush = virtgpu_bo_flush;
    gpu->base.bo_ops.invalidate = virtgpu_bo_invalidate;

src/virtio/vulkan/vn_renderer_vtest.c

@@ -1073,6 +1073,8 @@ vtest_init(struct vtest *vtest)
    vtest->base.bo_ops.create_from_dma_buf = NULL;
    vtest->base.bo_ops.destroy = vtest_bo_destroy;
    vtest->base.bo_ops.export_dma_buf = vtest_bo_export_dma_buf;
+   vtest->base.bo_ops.export_sync_file =
+      vn_renderer_bo_export_sync_file_internal;
    vtest->base.bo_ops.map = vtest_bo_map;
    vtest->base.bo_ops.flush = vtest_bo_flush;
    vtest->base.bo_ops.invalidate = vtest_bo_invalidate;