[kvm-devel] [PATCH] x86: handle double and triple faults for every exception

[Joerg R. <joe...@am...>]

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 <joe...@am...>
Cc: Jan Kiszka <jan...@si...>
---
 arch/x86/kvm/x86.c |   31 +++++++++++++++++--------------
 1 files changed, 17 insertions(+), 14 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 578a0c1..c05aa32 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -144,9 +144,21 @@ void kvm_set_apic_base(struct kvm_vcpu *vcpu, u64 data)
 }
 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;
@@ -157,25 +169,16 @@ void kvm_inject_page_fault(struct kvm_vcpu *vcpu, unsigned long addr,
 			   u32 error_code)
 {
 	++vcpu->stat.pf_guest;
-	if (vcpu->arch.exception.pending) {
-		if (vcpu->arch.exception.nr == PF_VECTOR) {
-			printk(KERN_DEBUG "kvm: inject_page_fault:"
-					" double fault 0x%lx\n", addr);
-			vcpu->arch.exception.nr = DF_VECTOR;
-			vcpu->arch.exception.error_code = 0;
-		} else if (vcpu->arch.exception.nr == DF_VECTOR) {
-			/* triple fault -> shutdown */
-			set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests);
-		}
-		return;
-	}
 	vcpu->arch.cr2 = addr;
 	kvm_queue_exception_e(vcpu, PF_VECTOR, error_code);
 }
 
 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;
-- 
1.5.3.7