From b936d3eb92b7c1258805bebecc7eaac0c8a51b7f Mon Sep 17 00:00:00 2001 From: Sean Christopherson Date: Wed, 23 Sep 2020 09:50:46 -0700 Subject: [PATCH] KVM: VMX: Unconditionally clear CPUID.INVPCID if !CPUID.PCID If PCID is not exposed to the guest, clear INVPCID in the guest's CPUID even if the VMCS INVPCID enable is not supported. This will allow consolidating the secondary execution control adjustment code without having to special case INVPCID. Technically, this fixes a bug where !CPUID.PCID && CPUID.INVCPID would result in unexpected guest behavior (#UD instead of #GP/#PF), but KVM doesn't support exposing INVPCID if it's not supported in the VMCS, i.e. such a config is broken/bogus no matter what. Signed-off-by: Sean Christopherson Message-Id: <20200923165048.20486-3-sean.j.christopherson@intel.com> Signed-off-by: Paolo Bonzini --- arch/x86/kvm/vmx/vmx.c | 16 +++++++++++----- 1 file changed, 11 insertions(+), 5 deletions(-) diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c index 96adc964afed..641e5ef513ae 100644 --- a/arch/x86/kvm/vmx/vmx.c +++ b/arch/x86/kvm/vmx/vmx.c @@ -4158,16 +4158,22 @@ static void vmx_compute_secondary_exec_control(struct vcpu_vmx *vmx) } } + /* + * Expose INVPCID if and only if PCID is also exposed to the guest. + * INVPCID takes a #UD when it's disabled in the VMCS, but a #GP or #PF + * if CR4.PCIDE=0. Enumerating CPUID.INVPCID=1 would lead to incorrect + * behavior from the guest perspective (it would expect #GP or #PF). + */ + if (!guest_cpuid_has(vcpu, X86_FEATURE_PCID)) + guest_cpuid_clear(vcpu, X86_FEATURE_INVPCID); + if (cpu_has_vmx_invpcid()) { /* Exposing INVPCID only when PCID is exposed */ bool invpcid_enabled = - guest_cpuid_has(vcpu, X86_FEATURE_INVPCID) && - guest_cpuid_has(vcpu, X86_FEATURE_PCID); + guest_cpuid_has(vcpu, X86_FEATURE_INVPCID); - if (!invpcid_enabled) { + if (!invpcid_enabled) exec_control &= ~SECONDARY_EXEC_ENABLE_INVPCID; - guest_cpuid_clear(vcpu, X86_FEATURE_INVPCID); - } if (nested) { if (invpcid_enabled) -- 2.34.1