KVM: x86: Handle triple fault in L2 without killing L1
Synthesize a nested VM-Exit if L2 triggers an emulated triple fault
instead of exiting to userspace, which likely will kill L1. Any flow
that does KVM_REQ_TRIPLE_FAULT is suspect, but the most common scenario
for L2 killing L1 is if L0 (KVM) intercepts a contributory exception that
is _not_intercepted by L1. E.g. if KVM is intercepting #GPs for the
VMware backdoor, a #GP that occurs in L2 while vectoring an injected #DF
will cause KVM to emulate triple fault.
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Cc: Jim Mattson <jmattson@google.com>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Message-Id: <20210302174515.2812275-2-seanjc@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 5c235b4..9bfec7e 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -8329,6 +8329,19 @@ static void update_cr8_intercept(struct kvm_vcpu *vcpu)
static_call(kvm_x86_update_cr8_intercept)(vcpu, tpr, max_irr);
}
+int kvm_check_nested_events(struct kvm_vcpu *vcpu)
+{
+ if (WARN_ON_ONCE(!is_guest_mode(vcpu)))
+ return -EIO;
+
+ if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
+ kvm_x86_ops.nested_ops->triple_fault(vcpu);
+ return 1;
+ }
+
+ return kvm_x86_ops.nested_ops->check_events(vcpu);
+}
+
static void inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit)
{
int r;
@@ -8374,7 +8387,7 @@ static void inject_pending_event(struct kvm_vcpu *vcpu, bool *req_immediate_exit
* from L2 to L1.
*/
if (is_guest_mode(vcpu)) {
- r = kvm_x86_ops.nested_ops->check_events(vcpu);
+ r = kvm_check_nested_events(vcpu);
if (r < 0)
goto busy;
}
@@ -8937,10 +8950,14 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
goto out;
}
if (kvm_check_request(KVM_REQ_TRIPLE_FAULT, vcpu)) {
- vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
- vcpu->mmio_needed = 0;
- r = 0;
- goto out;
+ if (is_guest_mode(vcpu)) {
+ kvm_x86_ops.nested_ops->triple_fault(vcpu);
+ } else {
+ vcpu->run->exit_reason = KVM_EXIT_SHUTDOWN;
+ vcpu->mmio_needed = 0;
+ r = 0;
+ goto out;
+ }
}
if (kvm_check_request(KVM_REQ_APF_HALT, vcpu)) {
/* Page is swapped out. Do synthetic halt */
@@ -9238,7 +9255,7 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu)
{
if (is_guest_mode(vcpu))
- kvm_x86_ops.nested_ops->check_events(vcpu);
+ kvm_check_nested_events(vcpu);
return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
!vcpu->arch.apf.halted);