KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is active (9167ab79) · Commits · 戴 / test

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>

arch/x86/kvm/svm.c

+8 −2

Original line number	Diff line number	Diff line
		@@ -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))

		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);

arch/x86/kvm/vmx/vmx.c

+3 −11

Original line number	Diff line number	Diff line
		@@ -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))
		/* Shadow paging assumes NX to be available. */
		if (!enable_ept)
		guest_efer \|= EFER_NX;
		else if (!(guest_efer & EFER_NX))
		ignore_bits \|= EFER_NX;
		}

		/*
		* LMA and LME handled by hardware; SCE meaningless outside long mode.

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