[Bug] virtio-gpu broken with qemu/kvm on arm64 on kernel 5.5+

[Chia-I Wu]

On Fri, Feb 21, 2020 at 2:06 AM Guillaume Gardet
<Guillaume.Gardet at arm.com> wrote:
>
> Hi,
>
> > -----Original Message-----
> > From: Chia-I Wu <olvaffe at gmail.com>
> > Sent: 20 February 2020 19:41
> > To: Guillaume Gardet <Guillaume.Gardet at arm.com>
> > Cc: dri-devel at lists.freedesktop.org; Gerd Hoffmann <kraxel at redhat.com>;
> > Daniel Vetter <daniel.vetter at ffwll.ch>; Catalin Marinas
> > <Catalin.Marinas at arm.com>; nd <nd at arm.com>
> > Subject: Re: [Bug] virtio-gpu broken with qemu/kvm on arm64 on kernel 5.5+
> >
> > On Thu, Feb 20, 2020 at 4:44 AM Guillaume Gardet <Guillaume.Gardet at arm.com>
> > wrote:
> > >
> > > Hi,
> > >
> > > With (guest) kernel 5.5+ with qemu/kvm on arm64, I get lots of display
> > corruptions leading to this kind of screen:
> > > https://openqa.opensuse.org/tests/1174521#step/yast2_i/24
> > Looking at the screenshot, it seems cacheline-related?
>
> It could be.
>
> >
> > There was a change of memory type
> >
> >   https://lists.freedesktop.org/archives/dri-devel/2019-August/233456.html
> >
> > While the guest memory type is ignored on Intel, it is honored on ARM.
> > This attempt to fix it
> >
> >   https://lists.freedesktop.org/archives/dri-devel/2019-December/248271.html
> >
> > does not seem to land.
>
> I applied this patch on top of 5.5.4, but it does not fix the problem.
> Maybe more similar changes are required?
The patch looks legit.  Maybe the memory type is not the root cause?