i915 "GPU HANG", bisected to a2daa27c0c61 "swiotlb: simplify swiotlb_max_segment"

[Marek Marczykowski-Górecki]

On Tue, Oct 18, 2022 at 10:24:13AM +0200, Christoph Hellwig wrote:
> On Tue, Oct 18, 2022 at 05:52:16AM +0200, Marek Marczykowski-Górecki wrote:
> > not only) when using IGD in Xen PV dom0. After not very long time Xorg
> > crashes, and dmesg contain messages like this:
> > 
> >     i915 0000:00:02.0: [drm] GPU HANG: ecode 7:1:01fffbfe, in Xorg [5337]
> >     i915 0000:00:02.0: [drm] Resetting rcs0 for stopped heartbeat on rcs0
> >     i915 0000:00:02.0: [drm] Xorg[5337] context reset due to GPU hang
> 
> <snip>
> 
> > I tried reverting just this commit on top of 6.0.x, but the context
> > changed significantly in subsequent commits, so after trying reverting
> > it together with 3 or 4 more commits I gave up.
> > 
> > What may be an important detail, the system heavily uses cross-VM shared
> > memory (gntdev) to map window contents from VMs. This is Qubes OS, and
> > it uses Xen 4.14.
> 
> Can you try the patch below?

Yes, this seems to help.

And since this is a PV domain, with Jan proposed change it should work
too. Intuitively this indeed should be PV-only thing (as was forcing
swiotlb before).

-- 
Best Regards,
Marek Marczykowski-Górecki
Invisible Things Lab
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