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

commit d6174299365ddbbf491620c0b8c5ca1a6ef2eea5 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/x86/kvm/mmu.h b/arch/x86/kvm/mmu.h
index e9688a9f7b579d521caeee89017d9b557397c652..7bb165c2323348647507631ece9a2c6029799619 100644 (file)
--- a/arch/x86/kvm/mmu.h
+++ b/arch/x86/kvm/mmu.h
@@ -49,6 +49,7 @@
                               X86_CR4_LA57)
 
 #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 61bc54748f221a57156351c68db4ed42357223b1..3e606a6940dc80b7fb1d3c75d4450cbd7b233662 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1605,8 +1605,7 @@ 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;