Hi,
> btw some questions here:
>
> for non-gl and gl rendering in Qemu, are they based on dma-buf already?
> once we can export guest framebuffer in dma-buf, is there additional work
> required or just straightforward to integrate with SPICE?
Right now we are busy integrating dma-buf support into spice, which will
be used for the gl rendering path, for virtio-gpu.
For intel-vgpu the wireup inside qemu will be slightly different: We'll
get a dma-buf handle from the igd driver, whereas virtio-gpu renders
into a texture, then exports that texture as dma-buf.
But in both cases we'll go pass the dma-buf with the guest framebuffer
(and meta-data such as fourcc and size) to spice-server, which in turn
will pass on the dma-buf to spice-client for (local) display. So we
have a common code path in spice for both virtio-gpu and intel-vgpu,
based on dma-bufs. spice-server even doesn't need to know what kind of
graphics device the guest has, it'll go just process the dma-bufs.
longer-term we also plan to support video-encoding for a remote display.
Again based on dma-bufs, by sending them to the gpu video encoder.
The non-gl rendering path needs to be figured out.
With virtio-gpu we'll go simply turn off 3d support, so the guest will
fallback to do software rendering, we'll get a classic DisplaySurface
and the vnc server can work with that.
That isn't going to fly with intel-vgpu though, so we need something
else. Import dma-buf, then glReadPixels into a DisplaySurface would
work. But as mentioned before I'd prefer a code path which doesn't
require opengl support in qemu, and one option for that would be the
special vfio region. I've written up a quick draft meanwhile:
diff --git a/include/uapi/linux/vfio.h b/include/uapi/linux/vfio.h
index 751b69f..91b928d 100644
--- a/include/uapi/linux/vfio.h
+++ b/include/uapi/linux/vfio.h
@@ -596,6 +596,28 @@ struct vfio_iommu_spapr_tce_remove {
};
#define VFIO_IOMMU_SPAPR_TCE_REMOVE _IO(VFIO_TYPE, VFIO_BASE + 20)
+/* -------- Additional API for vGPU -------- */
+
+/*
+ * framebuffer meta data
+ * subregion located at the end of the framebuffer region
+ */
+struct vfio_framebuffer {
+ __u32 argsz;
+
+ /* out */
+ __u32 format; /* drm fourcc */
+ __u32 offset; /* relative to region start */
+ __u32 width; /* in pixels */
+ __u32 height; /* in pixels */
+ __u32 stride; /* in bytes */
+
+ /* in+out */
+#define VFIO_FB_STATE_REQUEST_UPDATE 1 /* userspace requests update
*/
+#define VFIO_FB_STATE_UPDATE_COMPLETE 2 /* kernel signals completion
*/
+ __u32 state; /* VFIO_FB_STATE_ */
+};
+
/* ***************************************************************** */
#endif /* _UAPIVFIO_H */
cheers,
Gerd
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