@@ -498,19 +498,7 @@ static void kvm_multiple_exception(struct kvm_vcpu *vcpu,
vcpu->arch.exception.error_code = error_code;
vcpu->arch.exception.has_payload = has_payload;
vcpu->arch.exception.payload = payload;
- /*
- * In guest mode, payload delivery should be deferred,
- * so that the L1 hypervisor can intercept #PF before
- * CR2 is modified (or intercept #DB before DR6 is
- * modified under nVMX). However, for ABI
- * compatibility with KVM_GET_VCPU_EVENTS and
- * KVM_SET_VCPU_EVENTS, we can't delay payload
- * delivery unless userspace has enabled this
- * functionality via the per-VM capability,
- * KVM_CAP_EXCEPTION_PAYLOAD.
- */
- if (!vcpu->kvm->arch.exception_payload_enabled ||
- !is_guest_mode(vcpu))
+ if (!is_guest_mode(vcpu))
kvm_deliver_exception_payload(vcpu);
return;
}
@@ -3803,6 +3791,21 @@ static void kvm_vcpu_ioctl_x86_get_vcpu_events(struct kvm_vcpu *vcpu,
{
process_nmi(vcpu);
+ /*
+ * In guest mode, payload delivery should be deferred,
+ * so that the L1 hypervisor can intercept #PF before
+ * CR2 is modified (or intercept #DB before DR6 is
+ * modified under nVMX). Unless the per-VM capability,
+ * KVM_CAP_EXCEPTION_PAYLOAD, is set, we may not defer the delivery of
+ * an exception payload and handle after a KVM_GET_VCPU_EVENTS. Since we
+ * opportunistically defer the exception payload, deliver it if the
+ * capability hasn't been requested before processing a
+ * KVM_GET_VCPU_EVENTS.
+ */
+ if (!vcpu->kvm->arch.exception_payload_enabled &&
+ vcpu->arch.exception.pending && vcpu->arch.exception.has_payload)
+ kvm_deliver_exception_payload(vcpu);
+
/*
* The API doesn't provide the instruction length for software
* exceptions, so don't report them. As long as the guest RIP
KVM allows the deferral of exception payloads when a vCPU is in guest mode to allow the L1 hypervisor to intercept certain events (#PF, #DB) before register state has been modified. However, this behavior is incompatible with the KVM_{GET,SET}_VCPU_EVENTS ABI, as userspace expects register state to have been immediately modified. Userspace may opt-in for the payload deferral behavior with the KVM_CAP_EXCEPTION_PAYLOAD per-VM capability. As such, kvm_multiple_exception() will immediately manipulate guest registers if the capability hasn't been requested. Since the deferral is only necessary if a userspace ioctl were to be serviced at the same as a payload bearing exception is recognized, this behavior can be relaxed. Instead, opportunistically defer the payload from kvm_multiple_exception() and deliver the payload before completing a KVM_GET_VCPU_EVENTS ioctl. Signed-off-by: Oliver Upton <oupton@google.com> --- arch/x86/kvm/x86.c | 29 ++++++++++++++++------------- 1 file changed, 16 insertions(+), 13 deletions(-)