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

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commit 9167ab7993 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 <pbonzini@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: Joerg Roedel <jroedel@suse.de>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Paolo Bonzini 2019-10-27 09:36:37 +01:00 committed by Greg Kroah-Hartman
parent 37dfbc8ba7
commit db77548b16
2 changed files with 11 additions and 13 deletions
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10
arch/x86/kvm/svm.c
View file

@ -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);

14
arch/x86/kvm/vmx.c
View file

@ -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.