Re: [PATCH v4 0/2] x86/kvm/fpu: Fix guest migration bugs that can crash guest

[Leonardo Bras Soares Passos]

On Thu, Feb 17, 2022 at 11:52 AM Paolo Bonzini <pbonzini@xxxxxxxxxx> wrote:
>
> On 2/17/22 06:30, Leonardo Bras wrote:
> > This patchset comes from a bug I found during qemu guest migration from a
> > host with newer CPU to a host with an older version of this CPU, and thus
> > having less FPU features.
> >
> > When the guests were created, the one with less features is used as
> > config, so migration is possible.
> >
> > Patch 1 fix a bug that always happens during this migration, and is
> > related to the fact that xsave saves all feature flags, but xrstor does
> > not touch the PKRU flag. It also changes how fpstate->user_xfeatures
> > is set, going from kvm_check_cpuid() to the later called
> > kvm_vcpu_after_set_cpuid().
> >
> > Patch 2 removes kvm_vcpu_arch.guest_supported_xcr0 since it now
> > duplicates guest_fpu.fpstate->user_xfeatures. Some wrappers were
> > introduced in order to make it easier to read the replaced version.
> >
> > Patches were compile-tested, and could fix the bug found.
>
> Queued, thanks (for 5.17 of course)!  For patch 2, I renamed the
> function to kvm_guest_supported_xcr0.
>
> Paolo
>

That's great!
Thanks Paolo!