Local Display Direct Flip Feature Discussion

[Zhang, Tina]

> -----Original Message-----
> From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> Sent: Friday, December 14, 2018 10:21 AM
> To: Zhang, Tina <tina.zhang at intel.com>
> Cc: intel-gvt-dev <intel-gvt-dev at lists.freedesktop.org>; Alex Williamson
> <alex.williamson at redhat.com>; Gerd Hoffmann <kraxel at redhat.com>; Wang,
> Zhi A <zhi.a.wang at intel.com>; Tian, Kevin <kevin.tian at intel.com>; Yuan, Hang
> <hang.yuan at intel.com>; Lv, Zhiyuan <zhiyuan.lv at intel.com>; He, Min
> <min.he at intel.com>; Wang, Hongbo <hongbo.wang at intel.com>; Vetter,
> Daniel <daniel.vetter at intel.com>
> Subject: Re: Local Display Direct Flip Feature Discussion
> 
> On 2018.12.13 17:17:38 +0800, Zhang, Tina wrote:
> > 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.
> > After the assignment, host kernel can directly help guest to update
> > the information to the display registers of the assigned display
> > resources. However, the only problem is how we return the DRM framebuffer
> id to host userspace.
> >
> >
> >
> > Currently, we have two options:
> >
> > 1.       Through “/sys/bus/pci/devices/0000:00:02.0/$UUID/intel_vgpu/
> > plane_id_index”
> >
> > With the proposed “plane_id_index” attribute, userspace can echo the plane
> number to the attribute and then use cat to dump the userspace id of the DRM
> framebuffer standing for that vGPU’s plane in the host-side.
> 
> I had sent NACK on this, so pls move forward on ioctl way.
I suggest keeping this under debugfs. It will be helpful for debugging.

> 
> >
> > 2.       Through vfio ioctl:
> >
> > We can extend VFIO_DEVICE_QUERY_GFX_PLANE ABI by proposing
> > “VFIO_GFX_PLANE_TYPE_DRM_FB” type. So that vendor driver can return
> > the framebuffer id when userspace invoking
> > “VFIO_DEVICE_QUERY_GFX_PLANE” ioctl with flags as
> “VFIO_GFX_PLANE_TYPE_DRM_FB | VFIO_GFX_PLANE_TYPE_PROBE”
> >
> >
> >
> > The patches are on:
> >
> > https://github.com/intel/igvtg-qemu/tree/topic/local_display_direct_fl
> > ip
> >
> > https://github.com/intel/gvt-linux/tree/topic/local_display_direct_fli
> > p
> >
> 
> Could you send kernel patches for vfio ioctl change so we can review the design?
Sure.

BR,
Tina
> 
> thanks
> 
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