Re: [Xen-devel] [Intel-gfx] [Announcement] 2015-Q3 release of XenGT - a Mediated Graphics Passthrough Solution from Intel

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Tian, Kevin
> Sent: Friday, November 20, 2015 4:36 PM
> 
> >
> > > > So, for non-opengl rendering qemu needs the guest framebuffer data so it
> > > > can feed it into the vnc server.  The vfio framebuffer region is meant
> > > > to support this use case.
> > >
> > > what's the format requirement on that framebuffer? If you are familiar
> > > with Intel Graphics, there's a so-called tiling feature applied on frame
> > > buffer so it can't be used as a raw input to vnc server. w/o opengl you
> > > need do some conversion on CPU first.
> >
> > Yes, that conversion needs to happen, qemu can't deal with tiled
> > graphics.  Anything which pixman can handle will work.  Prefered would
> > be PIXMAN_x8r8g8b8 (aka DRM_FORMAT_XRGB8888 on little endian host) which
> > is the format used by the vnc server (and other places in qemu)
> > internally.

Now the format is reported based on guest setting. Some agent needs to
do format conversion in user space.

> >
> > qemu can also use the opengl texture for the guest fb, then fetch the
> > data with glReadPixels().  Which will probably do exactly the same
> > conversion.  But it'll add a opengl dependency to the non-opengl
> > rendering path in qemu, would be nice if we can avoid that.
> >
> > While being at it:  When importing a dma-buf with a tiled framebuffer
> > into opengl (via eglCreateImageKHR + EGL_LINUX_DMA_BUF_EXT) I suspect we
> > have to pass in the tile size as attribute to make it work.  Is that
> > correct?
> >
> 
> I'd guess so, but need double confirm later when reaching that level of 
> detail.
> some homework on dma-buf is required first. :-)
> 

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?

Thanks
Kevin
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