KVM: x86: Reinitialize context if host userspace toggles EFER.LME

While the guest runs, EFER.LME cannot change unless CR0.PG is clear, and
therefore EFER.NX is the only bit that can affect the MMU role.  However,
set_efer accepts a host-initiated change to EFER.LME even with CR0.PG=1.
In that case, the MMU has to be reset.

Fixes: 11988499e62b ("KVM: x86: Skip EFER vs. guest CPUID checks for host-initiated writes")
Cc: stable@vger.kernel.org
Reviewed-by: Sean Christopherson <seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index 51faa2c76ca5fbc192687e1cd46bc83a8165754a..a5a50cfeffff534f1eaef30288f2bddd1c2e619b 100644 (file)
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -48,6 +48,7 @@
                               X86_CR4_SMEP | X86_CR4_SMAP | X86_CR4_PKE)
 
 #define KVM_MMU_CR0_ROLE_BITS (X86_CR0_PG | X86_CR0_WP)
+#define KVM_MMU_EFER_ROLE_BITS (EFER_LME | EFER_NX)
 
 static __always_inline u64 rsvd_bits(int s, int e)
 {

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0b95c379e2345d1081c6ea5abc3e0361922e37aa..b724273493d81d1902111ac89fdd5437ccb7879a 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1648,8 +1648,7 @@ static int set_efer(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
                return r;
        }
 
-       /* Update reserved bits */
-       if ((efer ^ old_efer) & EFER_NX)
+       if ((efer ^ old_efer) & KVM_MMU_EFER_ROLE_BITS)
                kvm_mmu_reset_context(vcpu);
 
        return 0;