On Thu, Jul 17, 2025 at 12:34:48PM +0200, Paolo Bonzini wrote: > Date: Thu, 17 Jul 2025 12:34:48 +0200 > From: Paolo Bonzini <pbonz...@redhat.com> > Subject: [PATCH] target/i386: do not expose ARCH_CAPABILITIES on AMD CPU > X-Mailer: git-send-email 2.50.1 > > KVM emulates the ARCH_CAPABILITIES on x86 for both Intel and AMD > cpus, although the IA32_ARCH_CAPABILITIES MSR is an Intel-specific > MSR and it makes no sense to emulate it on AMD. > > As a consequence, VMs created on AMD with qemu -cpu host and using > KVM will advertise the ARCH_CAPABILITIES feature and provide the > IA32_ARCH_CAPABILITIES MSR. This can cause issues (like Windows BSOD) > as the guest OS might not expect this MSR to exist on such cpus (the > AMD documentation specifies that ARCH_CAPABILITIES feature and MSR > are not defined on the AMD architecture). > > A fix was proposed in KVM code, however KVM maintainers don't want to > change this behavior that exists for 6+ years and suggest changes to be > done in QEMU instead. Therefore, hide the bit from "-cpu host": > migration of -cpu host guests is only possible between identical host > kernel and QEMU versions, therefore this is not a problematic breakage. > > If a future AMD machine does include the MSR, that would re-expose the > Windows guest bug; but it would not be KVM/QEMU's problem at that > point, as we'd be following a genuine physical CPU impl.
Make sense. > Reported-by: Alexandre Chartre <alexandre.char...@oracle.com> > Suggested-by: Daniel P. Berrangé <berra...@redhat.com> > Signed-off-by: Paolo Bonzini <pbonz...@redhat.com> > --- > target/i386/kvm/kvm.c | 6 +++++- > 1 file changed, 5 insertions(+), 1 deletion(-) Good to see this fix. Late but, Reviewed-by: Zhao Liu <zhao1....@intel.com>
