KVM: VMX: Fix comparison of guest efer with stale host value

update_transition_efer() masks out some efer bits when deciding whether
to switch the msr during guest entry; for example, NX is emulated using the
mmu so we don't need to disable it, and LMA/LME are handled by the hardware.

However, with shared msrs, the comparison is made against a stale value;
at the time of the guest switch we may be running with another guest's efer.

Fix by deferring the mask/compare to the actual point of guest entry.

Noted by Marcelo.

Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 106f9f1f78c0..ce677b20bf86 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -185,11 +185,11 @@ static void kvm_shared_msr_cpu_online(void)
                 locals->current_value[i] = shared_msrs_global.msrs[i].value;
 }
 
-void kvm_set_shared_msr(unsigned slot, u64 value)
+void kvm_set_shared_msr(unsigned slot, u64 value, u64 mask)
 {
         struct kvm_shared_msrs *smsr = &__get_cpu_var(shared_msrs);
 
-        if (value == smsr->current_value[slot])
+        if (((value ^ smsr->current_value[slot]) & mask) == 0)
                 return;
         smsr->current_value[slot] = value;
         wrmsrl(shared_msrs_global.msrs[slot].msr, value);