[PATCH v2 04/14] KVM: x86: Don't attempt VMWare emulation on #GP with non-zero error code

[Sean Christopherson]

The VMware backdoor hooks #GP faults on IN{S}, OUT{S}, and RDPMC, none
of which generate a non-zero error code for their #GP.  Re-injecting #GP
instead of attempting emulation on a non-zero error code will allow a
future patch to move #GP injection (for emulation failure) into
kvm_emulate_instruction() without having to plumb in the error code.

Reviewed-and-tested-by: Vitaly Kuznetsov <vkuzn...@redhat.com>
Reviewed-by: Liran Alon <liran.a...@oracle.com>
Signed-off-by: Sean Christopherson <sean.j.christopher...@intel.com>
---
 arch/x86/kvm/svm.c     | 10 +++++++++-
 arch/x86/kvm/vmx/vmx.c | 12 +++++++++++-
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 1f220a85514f..7242142573d6 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -2772,12 +2772,20 @@ static int gp_interception(struct vcpu_svm *svm)
 
        WARN_ON_ONCE(!enable_vmware_backdoor);
 
+       /*
+        * VMware backdoor emulation on #GP interception only handles IN{S},
+        * OUT{S}, and RDPMC, none of which generate a non-zero error code.
+        */
+       if (error_code) {
+               kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
+               return 1;
+       }
        er = kvm_emulate_instruction(vcpu,
                EMULTYPE_VMWARE | EMULTYPE_NO_UD_ON_FAIL);
        if (er == EMULATE_USER_EXIT)
                return 0;
        else if (er != EMULATE_DONE)
-               kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
+               kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
        return 1;
 }
 
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index 18286e5b5983..8a65e1122376 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -4509,12 +4509,22 @@ static int handle_exception_nmi(struct kvm_vcpu *vcpu)
 
        if (!vmx->rmode.vm86_active && is_gp_fault(intr_info)) {
                WARN_ON_ONCE(!enable_vmware_backdoor);
+
+               /*
+                * VMware backdoor emulation on #GP interception only handles
+                * IN{S}, OUT{S}, and RDPMC, none of which generate a non-zero
+                * error code on #GP.
+                */
+               if (error_code) {
+                       kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
+                       return 1;
+               }
                er = kvm_emulate_instruction(vcpu,
                        EMULTYPE_VMWARE | EMULTYPE_NO_UD_ON_FAIL);
                if (er == EMULATE_USER_EXIT)
                        return 0;
                else if (er != EMULATE_DONE)
-                       kvm_queue_exception_e(vcpu, GP_VECTOR, error_code);
+                       kvm_queue_exception_e(vcpu, GP_VECTOR, 0);
                return 1;
        }
 
-- 
2.22.0