KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is active

VMX already does so if the host has SMEP, in order to support the combination of
CR0.WP=1 and CR4.SMEP=1.  However, it is perfectly safe to always do so, and in
fact VMX already ends up running with EFER.NXE=1 on old processors that lack the
"load EFER" controls, because it may help avoiding a slow MSR write.  Removing
all the conditionals simplifies the code.

SVM does not have similar code, but it should since recent AMD processors do
support SMEP.  So this patch also makes the code for the two vendors more similar
while fixing NPT=0, CR0.WP=1 and CR4.SMEP=1 on AMD processors.

Cc: stable@vger.kernel.org
Cc: Joerg Roedel <jroedel@suse.de>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index ca200b50cde4d1a178a47099e02e164b7a29e840..c5673bda4b66df5e7672abc78e5bf520b3c3361c 100644 (file)
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -734,8 +734,14 @@ static int get_npt_level(struct kvm_vcpu *vcpu)
 static void svm_set_efer(struct kvm_vcpu *vcpu, u64 efer)
 {
        vcpu->arch.efer = efer;
-       if (!npt_enabled && !(efer & EFER_LMA))
-               efer &= ~EFER_LME;
+
+       if (!npt_enabled) {
+               /* Shadow paging assumes NX to be available.  */
+               efer |= EFER_NX;
+
+               if (!(efer & EFER_LMA))
+                       efer &= ~EFER_LME;
+       }
 
        to_svm(vcpu)->vmcb->save.efer = efer | EFER_SVME;
        mark_dirty(to_svm(vcpu)->vmcb, VMCB_CR);

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 8f01019295a106d8689b9e51ad7b060004d829c3..5d21a4ab28cfc80b3f800adfd042cb23c155a737 100644 (file)
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -969,17 +969,9 @@ static bool update_transition_efer(struct vcpu_vmx *vmx, int efer_offset)
        u64 guest_efer = vmx->vcpu.arch.efer;
        u64 ignore_bits = 0;
 
-       if (!enable_ept) {
-               /*
-                * NX is needed to handle CR0.WP=1, CR4.SMEP=1.  Testing
-                * host CPUID is more efficient than testing guest CPUID
-                * or CR4.  Host SMEP is anyway a requirement for guest SMEP.
-                */
-               if (boot_cpu_has(X86_FEATURE_SMEP))
-                       guest_efer |= EFER_NX;
-               else if (!(guest_efer & EFER_NX))
-                       ignore_bits |= EFER_NX;
-       }
+       /* Shadow paging assumes NX to be available.  */
+       if (!enable_ept)
+               guest_efer |= EFER_NX;
 
        /*
         * LMA and LME handled by hardware; SCE meaningless outside long mode.