[PATCH 3/3] [AMD] Skip instruction on a task switch only when appropriate.

[Gleb Natapov <gleb@redhat.com>]

If a task switch was initiated because off a task gate in IDT and IDT
was accessed because of an external even the instruction should not
be skipped.

Signed-off-by: Gleb Natapov <gleb@redhat.com>
---

 arch/x86/kvm/svm.c |   11 +++++++++--
 1 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 3ffb695..053f3c5 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -1826,6 +1826,7 @@ static int task_switch_interception(struct vcpu_svm *svm,
 	int reason;
 	int int_type = svm->vmcb->control.exit_int_info &
 		SVM_EXITINTINFO_TYPE_MASK;
+	int int_vec = svm->vmcb->control.exit_int_info & SVM_EVTINJ_VEC_MASK;
 
 	tss_selector = (u16)svm->vmcb->control.exit_info_1;
 
@@ -1841,8 +1842,14 @@ static int task_switch_interception(struct vcpu_svm *svm,
 		reason = TASK_SWITCH_CALL;
 
 
-	if (reason != TASK_SWITCH_GATE || int_type == SVM_EXITINTINFO_TYPE_SOFT)
-		skip_emulated_instruction(&svm->vcpu);
+	if (reason != TASK_SWITCH_GATE ||
+	    int_type == SVM_EXITINTINFO_TYPE_SOFT ||
+	    (int_type == SVM_EXITINTINFO_TYPE_EXEPT &&
+	     (int_vec == OF_VECTOR || int_vec == BP_VECTOR))) {
+		if (emulate_instruction(&svm->vcpu, kvm_run, 0, 0,
+					EMULTYPE_SKIP) != EMULATE_DONE)
+			return 0;
+	}
 
 	return kvm_task_switch(&svm->vcpu, tss_selector, reason);
 }