[patch 1/2] KVM: x86: handle double and triple faults for every exception

[Marcelo Tosatti <mtosatti@redhat.com>]

[-- Attachment #1: handle-multiple-exceptions --]
[-- Type: text/plain, Size: 2276 bytes --]

From: Joerg Roedel <joerg.roedel@amd.com>

The current KVM x86 exception code handles double and triple faults only for
page fault exceptions. This patch extends this detection for every exception
that gets queued for the guest.

Signed-off-by: Joerg Roedel <joerg.roedel@amd.com>
CC: Jan Kiszka <jan.kiszka@web.de>

Index: kvm/arch/x86/kvm/x86.c
===================================================================
--- kvm.orig/arch/x86/kvm/x86.c
+++ kvm/arch/x86/kvm/x86.c
@@ -170,9 +170,21 @@ void kvm_set_apic_base(struct kvm_vcpu *
 }
 EXPORT_SYMBOL_GPL(kvm_set_apic_base);
 
+static void handle_multiple_faults(struct kvm_vcpu *vcpu)
+{
+       if (vcpu->arch.exception.nr != DF_VECTOR) {
+               vcpu->arch.exception.nr = DF_VECTOR;
+               vcpu->arch.exception.error_code = 0;
+       } else
+               set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
+}
+
 void kvm_queue_exception(struct kvm_vcpu *vcpu, unsigned nr)
 {
-	WARN_ON(vcpu->arch.exception.pending);
+	if (vcpu->arch.exception.pending) {
+		handle_multiple_faults(vcpu);
+		return;
+	}
 	vcpu->arch.exception.pending = true;
 	vcpu->arch.exception.has_error_code = false;
 	vcpu->arch.exception.nr = nr;
@@ -184,24 +196,6 @@ void kvm_inject_page_fault(struct kvm_vc
 {
 	++vcpu->stat.pf_guest;
 
-	if (vcpu->arch.exception.pending) {
-		switch(vcpu->arch.exception.nr) {
-		case DF_VECTOR:
-			/* triple fault -> shutdown */
-			set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
-			return;
-		case PF_VECTOR:
-			vcpu->arch.exception.nr = DF_VECTOR;
-			vcpu->arch.exception.error_code = 0;
-			return;
-		default:
-			/* replace previous exception with a new one in a hope
-			   that instruction re-execution will regenerate lost
-			   exception */
-			vcpu->arch.exception.pending = false;
-			break;
-		}
-	}
 	vcpu->arch.cr2 = addr;
 	kvm_queue_exception_e(vcpu, PF_VECTOR, error_code);
 }
@@ -214,7 +208,10 @@ EXPORT_SYMBOL_GPL(kvm_inject_nmi);
 
 void kvm_queue_exception_e(struct kvm_vcpu *vcpu, unsigned nr, u32 error_code)
 {
-	WARN_ON(vcpu->arch.exception.pending);
+	if (vcpu->arch.exception.pending) {
+		handle_multiple_faults(vcpu);
+		return;
+	}
 	vcpu->arch.exception.pending = true;
 	vcpu->arch.exception.has_error_code = true;
 	vcpu->arch.exception.nr = nr;

--