[RFC PATCH 2/7] drm/i915/gvt: Use meta fbs to stand for vGPU's planes

[Zhang, Tina]

> -----Original Message-----
> From: Zhenyu Wang [mailto:zhenyuw at linux.intel.com]
> Sent: Monday, December 3, 2018 4:36 PM
> To: Zhang, Tina <tina.zhang at intel.com>
> Cc: intel-gfx at lists.freedesktop.org; Kondapally, Kalyan
> <kalyan.kondapally at intel.com>; intel-gvt-dev at lists.freedesktop.org; Wang, Zhi
> A <zhi.a.wang at intel.com>
> Subject: Re: [RFC PATCH 2/7] drm/i915/gvt: Use meta fbs to stand for vGPU's
> planes
> 
> On 2018.12.03 16:21:04 +0800, Zhenyu Wang wrote:
> > On 2018.12.03 15:35:17 +0800, Tina Zhang wrote:
> > > Create and initialize vGPU meta framebuffers during vGPU's creation.
> > > Each meta framebuffer is an intel_framebuffer. Userspace can get the
> > > userspace visible identifier of that meta framebuffer by accessing
> > > plane_id_index attribute.
> > >
> > > For example:
> > > In "/sys/bus/pci/devices/0000\:00\:02.0/$vGPU_id/intel_vgpu/"
> > > directory,
> > >
> > >    /* plane_id_index: pipe#(bit16:8) and plane#(bit7:0)*/
> > >    echo "0x10" > plane_index_id //Set the index to the plane 0 of
> > > pipe 1
> > >
> > >    /*
> > >     * Dump userspace visible identifier of the meta framebuffer
> > >     * standing for the primary plane of the vGPU's pipe one
> > >     */
> > >    cat plane_index_id //dump the id for plane 0 of pipe 1
> > >
> > > Then userspace can use this id with the exsting KMS IOCTL, e.g.
> > > drmModeSetPlane, to assign a physical plane to this virtual plane.
> >
> > How does user know which plane/pipe is active for vGPU? Looks from
> > current code it has no way to know that. I think for guest display
> > assignment, we need to know the display state of vGPU and it looks
> > there's no state tracking, e.g what if guest driver switches to
> > another plane for display? How could user know that then adjust for
> > assignment?
> >
> > And really don't like sysfs to r/w file for id, even if doesn't use
> > vfio gfx dmabuf interface for guest display object presentation, a
> > vendor specific vfio device ioctl if possible is better.
> >
> 
> And add that this device specific info sysfs is created when mdev device created
> before it's opened for vGPU instance. So I don't think it's proper place to put
> display config info.
It's actually one of the intel_vgpu attributes. And it's created during vGPU being created.
Thanks.

BR,
Tina
> 
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