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KVM: VMX: Refuse to load kvm_intel if EPT and NX are disabled

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Refuse to load KVM if NX support is not available and EPT is not enabled.
Shadow paging has assumed NX support since commit 9167ab7993 ("KVM:
vmx, svm: always run with EFER.NXE=1 when shadow paging is active"), so
for all intents and purposes this has been a de facto requirement for
over a year.

Do not require NX support if EPT is enabled purely because Intel CPUs let
firmware disable NX support via MSR_IA32_MISC_ENABLES.  If not for that,
VMX (and KVM as a whole) could require NX support with minimal risk to
breaking userspace.

Fixes: 9167ab7993 ("KVM: vmx, svm: always run with EFER.NXE=1 when shadow paging is active")
Signed-off-by: Sean Christopherson <seanjc@google.com>
Reviewed-by: Jim Mattson <jmattson@google.com>
Message-Id: <20210615164535.2146172-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Sean Christopherson 2021-06-15 09:45:32 -07:00 committed by Paolo Bonzini
parent f1b8325508
commit 23f079c249
1 changed files with 6 additions and 0 deletions
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6
arch/x86/kvm/vmx/vmx.c
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@ -7723,6 +7723,12 @@ static __init int hardware_setup(void)
!cpu_has_vmx_invept_global())
enable_ept = 0;
/* NX support is required for shadow paging. */
if (!enable_ept && !boot_cpu_has(X86_FEATURE_NX)) {
pr_err_ratelimited("kvm: NX (Execute Disable) not supported\n");
return -EOPNOTSUPP;
}
if (!cpu_has_vmx_ept_ad_bits() || !enable_ept)
enable_ept_ad_bits = 0;