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Subject[PATCH v2 04/14] KVM: x86: Don't attempt VMWare emulation on #GP with non-zero error code
Date
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 <vkuznets@redhat.com>
Reviewed-by: Liran Alon <liran.alon@oracle.com>
Signed-off-by: Sean Christopherson <sean.j.christopherson@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
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