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 9ae6168d381e2ec1f31d104fc80d41f6b2909058..f502fa3cb3b47a0c0c7a5694b02ef31f05d5c992 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 e8f495b9ae1037fe0e93e95fc0c2d17bc8d867cd..ff181a6c1005f63c6eb5e47ce3007cf830d40cb4 100644 (file)
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1614,8 +1614,7 @@ 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;