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Re: [Xen-devel] Xen fails to resume on AMD Fam15h (and Fam17h?) because of CPUID mismatch

On 10.02.2020 00:06, Marek Marczykowski-Górecki wrote:
> Hi,
> Multiple Qubes users have reported issues with resuming from S3 on AMD
> systems (Ryzen 2500U, Ryzen Pro 3700U, maybe more). The error message
> is:
> (XEN) CPU0: cap[ 1] is 7ed8320b (expected f6d8320b)
> If I read it right, this is:
>   - OSXSAVE: 0 -> 1
>   - HYPERVISOR: 1 -> 0
> Commenting out the panic on a failed recheck_cpu_features() in power.c
> makes the system work after resume, reportedly stable. But that doesn't
> sounds like a good idea generally.
> Is this difference a Xen fault (some missing MSR / other register
> restore on resume)? Or BIOS vendor / AMD, that could be worked around in
> Xen?

The transition of the HYPERVISOR bit is definitely a Xen issue,
with Andrew having sent a patch already (iirc). The OSXSAVE part
is a little more surprising, as I wouldn't think behavior there
should differ between Intel and AMD. I take your report though
to imply that you see the issue on AMD systems only? (You also
don't mention the Xen version, which may matter as there may
have been ordering changes of when the full original CR4 value
gets restored.)


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