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SubjectRe: [PATCH 0/3] KVM: x86: Fix XSAVE related bugs
* Sean Christopherson (seanjc@google.com) wrote:
> Patch 2 (from Dave) is the headliner and fixes a bug where KVM clear the
> FP+SSE bits in user_xfeatures when XSAVE is hidden from the guest and thus
> prevent userspace from saving/restoring FP+SSE state on XSAVE host. This
> most visibily manifests as a failed migration (KVM_GET_XSAVE succeeds on a
> non-XSAVE host and KVM_SET_XSAVE fails on an XSAVE host), but also causes
> KVM_GET_SAVE on XSAVE hosts to effectively corrupt guest FP+SSE state.
>
> Patch 1 fixes a mostly theoretical bug, and is also a prerequisite for
> patch 2.
>
> Patch 3 fixes a bug found by inspection when staring at all of this. KVM
> fails to check CR4.OSXSAVE when emulating XSETBV (the interception case
> gets away without the check because the intercept happens after hardware
> checks CR4).

Thanks for pulling those together; the set of 3 passes my same (light) smoke test.

Dave
>
> Dr. David Alan Gilbert (1):
> KVM: x86: Always enable legacy FP/SSE in allowed user XFEATURES
>
> Sean Christopherson (2):
> KVM: x86: Reinstate kvm_vcpu_arch.guest_supported_xcr0
> KVM: x86: Inject #UD on emulated XSETBV if XSAVES isn't enabled
>
> arch/x86/include/asm/kvm_host.h | 1 +
> arch/x86/kvm/cpuid.c | 11 ++++++++---
> arch/x86/kvm/emulate.c | 3 +++
> arch/x86/kvm/x86.c | 10 +++-------
> 4 files changed, 15 insertions(+), 10 deletions(-)
>
>
> base-commit: 372d07084593dc7a399bf9bee815711b1fb1bcf2
> --
> 2.37.1.595.g718a3a8f04-goog
>
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK

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