[PATCH RFC 29/39] KVM: x86/xen: evtchn unmask support

[Joao Martins <joao.m.martins@oracle.com>]

From: Ankur Arora <ankur.a.arora@oracle.com>

Handle hypercall to unmasks event channel ports.

A subtlety here is that we deliver an upcall if an actual unmask
happened and the event channel was pending (and if the vcpu-wide
evtchn_pending_sel was not already marked pending.)

Co-developed-by: Joao Martins <joao.m.martins@oracle.com>
Signed-off-by: Ankur Arora <ankur.a.arora@oracle.com>
Signed-off-by: Joao Martins <joao.m.martins@oracle.com>
---
 arch/x86/kvm/xen.c | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/arch/x86/kvm/xen.c b/arch/x86/kvm/xen.c
index 420e3ebb66bc..1988ed3866bf 100644
--- a/arch/x86/kvm/xen.c
+++ b/arch/x86/kvm/xen.c
@@ -2102,6 +2102,29 @@ static int shim_hcall_evtchn_send(struct kvm_xen *dom0, struct evtchn_send *snd)
 	return 0;
 }
 
+static int shim_hcall_evtchn_unmask(struct kvm_xen *dom0, int port)
+{
+	struct shared_info *s = HYPERVISOR_shared_info;
+	struct evtchnfd *evtchnfd;
+	struct vcpu_info *v;
+
+	evtchnfd = idr_find(&dom0->port_to_evt, port);
+	if (!evtchnfd)
+		return -ENOENT;
+
+	v = per_cpu(xen_vcpu, evtchnfd->vcpu);
+
+	if (test_and_clear_bit(port, (unsigned long *) s->evtchn_mask) &&
+	    test_bit(port, (unsigned long *) s->evtchn_pending) &&
+	    !test_and_set_bit(port / BITS_PER_EVTCHN_WORD,
+			      (unsigned long *) &v->evtchn_pending_sel)) {
+		kvm_xen_evtchn_2l_vcpu_set_pending(v);
+		return kvm_xen_evtchn_call_function(evtchnfd);
+	}
+
+	return 0;
+}
+
 static int shim_hcall_evtchn(int op, void *p)
 {
 	int ret;
@@ -2151,6 +2174,13 @@ static int shim_hcall_evtchn(int op, void *p)
 		un->port = evt.port;
 		break;
 	}
+	case EVTCHNOP_unmask: {
+		struct evtchn_unmask *unmask;
+
+		unmask = (struct evtchn_unmask *) p;
+		ret = shim_hcall_evtchn_unmask(xen_shim, unmask->port);
+		break;
+	}
 	case EVTCHNOP_send: {
 		struct evtchn_send *send;
 
-- 
2.11.0