[Qemu-devel] [PATCH v2 2/2] i386/kvm: lower requirements for Hyper-V frequency MSRs exposure

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Requiring tsc_is_stable_and_known() is too restrictive: even without INVTCS
nested Hyper-V-on-KVM enables TSC pages for its guests e.g. when
Reenlightenment MSRs are present. Presence of frequency MSRs doesn't mean
these frequencies are stable, it just means they're available for reading.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
---
 target/i386/kvm.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/target/i386/kvm.c b/target/i386/kvm.c
index accf50eac3..a6d1210f46 100644
--- a/target/i386/kvm.c
+++ b/target/i386/kvm.c
@@ -650,7 +650,7 @@ static int hyperv_handle_properties(CPUState *cs)
         env->features[FEAT_HYPERV_EAX] |= HV_TIME_REF_COUNT_AVAILABLE;
         env->features[FEAT_HYPERV_EAX] |= HV_REFERENCE_TSC_AVAILABLE;
 
-        if (has_msr_hv_frequencies && tsc_is_stable_and_known(env)) {
+        if (has_msr_hv_frequencies && env->tsc_khz) {
             env->features[FEAT_HYPERV_EAX] |= HV_ACCESS_FREQUENCY_MSRS;
             env->features[FEAT_HYPERV_EDX] |= HV_FREQUENCY_MSRS_AVAILABLE;
         }
-- 
2.14.3