From db77548b16521501a287f0e5c8e7754ba35c0193 Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Sun, 27 Oct 2019 09:36:37 +0100 Subject: [PATCH] KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is active commit 9167ab79936206118cc60e47dcb926c3489f3bd5 upstream. 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 also 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. SVM does not have similar code, but it should since recent AMD processors do support SMEP. So this patch makes the code for the two vendors simpler and more similar, while fixing an issue with CR0.WP=1 and CR4.SMEP=1 on AMD. Signed-off-by: Paolo Bonzini Signed-off-by: Thomas Gleixner Cc: Joerg Roedel Cc: stable@vger.kernel.org Signed-off-by: Greg Kroah-Hartman --- arch/x86/kvm/svm.c | 10 ++++++++-- arch/x86/kvm/vmx.c | 14 +++----------- 2 files changed, 11 insertions(+), 13 deletions(-) diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c index ac2cc2ed7a85..7657dcd72134 100644 --- a/arch/x86/kvm/svm.c +++ b/arch/x86/kvm/svm.c @@ -736,8 +736,14 @@ 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.c b/arch/x86/kvm/vmx.c index 6f7b3acdab26..4eda2a9c234a 100644 --- a/arch/x86/kvm/vmx.c +++ b/arch/x86/kvm/vmx.c @@ -2785,17 +2785,9 @@ 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. -- GitLab