@@ -389,6 +389,15 @@ uint32_t kvm_arch_get_supported_cpuid(KVMState *s, uint32_t function,
if (host_tsx_blacklisted()) {
ret &= ~(CPUID_7_0_EBX_RTM | CPUID_7_0_EBX_HLE);
}
+ } else if (function == 7 && index == 0 && reg == R_EDX) {
+ /*
+ * Linux incorrectly v4.17-v4.20 return ARCH_CAPABILITIES on SVM.
+ * We can detect the bug by checking if MSR_IA32_ARCH_CAPABILITIES is
+ * returned by KVM_GET_MSR_INDEX_LIST.
+ */
+ if (!has_msr_arch_capabs) {
+ ret &= ~CPUID_7_0_EDX_ARCH_CAPABILITIES;
+ }
} else if (function == 0x80000001 && reg == R_ECX) {
/*
* It's safe to enable TOPOEXT even if it's not returned by
KVM has two bugs in the handling of MSR_IA32_ARCH_CAPABILITIES: 1) Linux commit commit 1eaafe91a0df ("kvm: x86: IA32_ARCH_CAPABILITIES is always supported") makes GET_SUPPORTED_CPUID return arch_capabilities even if running on SVM. This makes "-cpu host,migratable=off" incorrectly expose arch_capabilities on CPUID on AMD hosts (where the MSR is not emulated by KVM). 2) KVM_GET_MSR_INDEX_LIST does not return MSR_IA32_ARCH_CAPABILITIES if the MSR is not supported by the host CPU. This makes QEMU not initialize the MSR properly at kvm_put_msrs() on those hosts. Work around both bugs on the QEMU side, by checking if the MSR was returned by KVM_GET_MSR_INDEX_LIST before returning the feature flag on kvm_arch_get_supported_cpuid(). This has the unfortunate side effect of making arch_capabilities unavailable on hosts without hardware support for the MSR until bug #2 is fixed on KVM, but I can't see another way to work around bug #1 without that side effect. Signed-off-by: Eduardo Habkost <ehabkost@redhat.com> --- Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Jim Mattson <jmattson@google.com> Cc: KarimAllah Ahmed <karahmed@amazon.de> Cc: David Woodhouse <dwmw@amazon.co.uk> Cc: Darren Kenny <darren.kenny@oracle.com> --- target/i386/kvm.c | 9 +++++++++ 1 file changed, 9 insertions(+)