Re: [tip: ras/core] x86/mce: Enable additional error logging on certain Intel CPUs

[Jim Mattson <jmattson@xxxxxxxxxx>]

On Mon, Nov 9, 2020 at 2:09 PM Luck, Tony <tony.luck@xxxxxxxxx> wrote:
>
> What does KVM do with model specific MSRs?

"Model specific model-specific registers?" :-)

KVM only implements a small subset of MSRs. By default, any access to
the rest raises #GP.

> Looks like you let the guest believe it was running on one of Sandy Bridge, Ivy Bridge, Haswell (Xeon).
>
> So, the core MCE code tried to enable extended error reporting.
>
> If there is a mode to have KVM let the guest think that it read/wrote MSR 0x17F,
> but actually, doesn't do it ... that would seem to be a reasonable thing to do here.

There is an 'ignore_msrs' module parameter, to sink writes and return
zero on reads for unknown MSRs, but I don't think it's commonly used.

I thought Linux had long ago gone the route of turning rdmsr/wrmsr
into rdmsr_safe/wrmsr_safe, so that the guest would ignore the #GPs on
writes and return zero to the caller for #GPs on reads.