Local Display Direct Flip Feature Discussion

[Zhenyu Wang]

On 2018.12.13 13:33:50 +0100, Gerd Hoffmann wrote:
>   Hi,
> 
> > The proposed userspace interface:
> 
> > Each plane of the vGPU is exposed as a DRM framebuffer object in the
> > host-side during the vGPU creation. So host userspace can assign the
> > HW display planes to vGPU's planes by using existing DRM/KMS APIs.
> 
> --verbose please.
> 
> Isn't a framebuffer just a gem object with metadata (fourcc, width,
> height, stride, ...) attached?  So I'm wondering how that works in
> detail.  What happens on page-flip?  Do you make the framebuffer
> reference another gem object then?  Or do you blit the guest display
> to the framebuffer?
> 
> What happens when the guest switches the display resolution?
> 

I pushed my previous hack to use vfio gfx plane dmabuf object to
display directly on local monitor via drm API on
https://github.com/zhenyw/qemu/commit/79f4bffb504b4b808eb91ca3cc6df5c43a542f85

Hopefully that can give answers on your questions. Besides Tina's
proposal on direct flip of vGPU plane in kernel, we still need to
discuss on what's possibly for qemu's user interface to output vGPU
display directly on local monitor, e.g output choosing, coordinate
with possible other display manager, etc.

thanks

-- 
Open Source Technology Center, Intel ltd.

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