[PATCH 5/5] kvm/svm: kick L2 guest to L1 by ready async_pf

[Roman Kagan <rkagan@virtuozzo.com>]

When async pagefault is resolved vCPU may be executing L2 guest.

In order to allow L1 take better scheduling decisions in such cases,
make L2 exit to L1 on a fake external interupt, without actually
injecting it (unless L2 has other reasons to vmexit).

This patch does that for x86/AMD.

Signed-off-by: Roman Kagan <rkagan@virtuozzo.com>
---
Note 1: I didn't have a chance to test this; I'll do when I get access to an
AMD machine and let you know if anything goes wrong

Note 2: I mostly modelled this patch after the one for vmx but is looks not
very appealing for svm.  I'd appreciate being pointed at a better location
where to stick the fake external interrupt vmexit.

 arch/x86/kvm/svm.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index 8ca1eca..1f6ae15 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -3723,6 +3723,15 @@ static int mwait_interception(struct vcpu_svm *svm)
 	return nop_interception(svm);
 }
 
+static int svm_check_nested_events(struct kvm_vcpu *vcpu, bool external_intr)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	if (kvm_async_pf_has_ready(vcpu))
+		nested_svm_intr(svm);
+	return 0;
+}
+
 enum avic_ipi_failure_cause {
 	AVIC_IPI_FAILURE_INVALID_INT_TYPE,
 	AVIC_IPI_FAILURE_TARGET_NOT_RUNNING,
@@ -5406,6 +5415,7 @@ static struct kvm_x86_ops svm_x86_ops __ro_after_init = {
 
 	.check_intercept = svm_check_intercept,
 	.handle_external_intr = svm_handle_external_intr,
+	.check_nested_events = svm_check_nested_events,
 
 	.sched_in = svm_sched_in,
 
-- 
2.9.3