On Thu, 26 Apr 2018 08:14:27 +0200 Gerd Hoffmann <kraxel@redhat.com> wrote:
On Thu, Apr 26, 2018 at 03:44:15AM +0000, Tian, Kevin wrote:
From: Alex Williamson Sent: Thursday, April 19, 2018 2:32 AM
That almost begins to look reasonable, but then we can only expose this for mdev devices, what if we were to hack a back door into a directly assigned GPU that tracks the location of active display in the framebuffer and implement the GFX_PLANE interface for that? We have no sysfs representation for either the template or the actual device for anything other than mdev. This inconsistency with physically assigned devices has been one of my arguments against enhancing mdev sysfs.
One possible option is to wrap directly assigned GPU into a mdev. The parent driver could be a dummy PCI driver which does basic PCI initialization, and then provide hooks for vendor-specific hack.
Thowing amdgpu into the mix. Looks they have vgpu support too, but using sriov instead of mdev. Having VFIO_GFX support surely looks useful there. Adding a mdev dependency to the VFIO_GFX api would makes things more complicated there for (IMHO) no good reason ...
Yes, it may be that a device wanting to implement display or migration might take the mdev approach, but that should be a choice of the implementation, not a requirement imposed by the API. Thanks, Alex