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>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 06e0856..4f865e8 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -812,6 +812,6 @@
int kvm_cpu_get_interrupt(struct kvm_vcpu *v);
void kvm_define_shared_msr(unsigned index, u32 msr);
-void kvm_set_shared_msr(unsigned index, u64 val);
+void kvm_set_shared_msr(unsigned index, u64 val, u64 mask);
#endif /* _ASM_X86_KVM_HOST_H */
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index ed97c6c..d4918d6 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -89,6 +89,7 @@
struct shared_msr_entry {
unsigned index;
u64 data;
+ u64 mask;
};
struct vcpu_vmx {
@@ -601,12 +602,10 @@
if (guest_efer & EFER_LMA)
ignore_bits &= ~(u64)EFER_SCE;
#endif
- if ((guest_efer & ~ignore_bits) == (host_efer & ~ignore_bits))
- return false;
-
guest_efer &= ~ignore_bits;
guest_efer |= host_efer & ignore_bits;
vmx->guest_msrs[efer_offset].data = guest_efer;
+ vmx->guest_msrs[efer_offset].mask = ~ignore_bits;
return true;
}
@@ -657,7 +656,8 @@
#endif
for (i = 0; i < vmx->save_nmsrs; ++i)
kvm_set_shared_msr(vmx->guest_msrs[i].index,
- vmx->guest_msrs[i].data);
+ vmx->guest_msrs[i].data,
+ vmx->guest_msrs[i].mask);
}
static void __vmx_load_host_state(struct vcpu_vmx *vmx)
@@ -2394,6 +2394,7 @@
data = data_low | ((u64)data_high << 32);
vmx->guest_msrs[j].index = i;
vmx->guest_msrs[j].data = 0;
+ vmx->guest_msrs[j].mask = -1ull;
++vmx->nmsrs;
}
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 106f9f1..ce677b2 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -185,11 +185,11 @@
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);