Re: [Xen-devel] Debugging Windows HVM crashes on Ryzen 3xxx series CPUs.

[Jürgen Groß <jgross@xxxxxxxx>]

On 25.10.19 19:01, Andrew Cooper wrote:
> On 24/10/2019 12:57, Steven Haigh wrote:
> > Hi all,
> >
> > I've managed to get the git master version of Xen on this affected
> > system and tries to boot a Windows Server 2016 system. It crashes as
> > per normal.
> >
> > I managed to get these logs, but I'm not quite sure what else to do to
> > debug this issue further.
> After a collaborative debugging session on IRC, we've identified the
> problem.  Here is a summary.
>
> https://www.reddit.com/r/Amd/comments/ckr5f4/amd_ryzen_3000_series_linux_support_and/
> is concerning KVM, but it identified that the TOPOEXT feature was
> important to getting windows to boot.
>
> Xen doesn't currently offer TOPOEXT to guests at all.  Fixing this is on
> the TODO list along with the rest of the topology representation swamp.
>
> On a hunch, I offered up a XenServer patch which we are still using, in
> lieu of fixing topology properly.  It is logically a revert of
> ca2eee92df44 as that change wasn't migration safe.
>
> With this patch in place, windows works fine.  However, I don't think
> the patch is appropriate to take into 4.13.
>
> Furthermore, there is no chance of getting the topology work sorted in
> the remaining 4.13 timeframe.
>
> I'm at a loss for ideas, other than release note it as broken and make
> fixing it a blocker for 4.14.
>
> Thoughts?
What about a domain config entry defaulting to "off" selecting the
topology modification in libxc you provided for the test? That would
just require to add a bool parameter to xc_cpuid_apply_policy(). It
might even be possible to select the setting on the affected hardware
automatically.


Juergen

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