[PATCH] kvm: nVMX: Relax guest IA32_FEATURE_CONTROL constraints

[Jim Mattson <jmattson@google.com>]

Commit 37e4c997dadf ("KVM: VMX: validate individual bits of guest
MSR_IA32_FEATURE_CONTROL") broke the KVM_SET_MSRS ABI by instituting
new constraints on the data values that kvm would accept for the guest
MSR, IA32_FEATURE_CONTROL. Perhaps these constraints should have been
opt-in via a new KVM capability, but they were applied
indiscriminately, breaking at least one existing hypervisor.

Relax the constraints to allow either or both of
FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX and
FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX to be set when nVMX is
enabled. This change is sufficient to fix the aforementioned breakage.

Fixes: 37e4c997dadf ("KVM: VMX: validate individual bits of guest MSR_IA32_FEATURE_CONTROL")
Signed-off-by: Jim Mattson <jmattson@google.com>
---
 arch/x86/kvm/vmx/vmx.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 04a8212704c17..9f46023451810 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -7097,10 +7097,12 @@ static void vmx_cpuid_update(struct kvm_vcpu *vcpu)
 
 	if (nested_vmx_allowed(vcpu))
 		to_vmx(vcpu)->msr_ia32_feature_control_valid_bits |=
+			FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX |
 			FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
 	else
 		to_vmx(vcpu)->msr_ia32_feature_control_valid_bits &=
-			~FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX;
+			~(FEATURE_CONTROL_VMXON_ENABLED_INSIDE_SMX |
+			  FEATURE_CONTROL_VMXON_ENABLED_OUTSIDE_SMX);
 
 	if (nested_vmx_allowed(vcpu)) {
 		nested_vmx_cr_fixed1_bits_update(vcpu);
-- 
2.24.0.432.g9d3f5f5b63-goog