xen/pv-on-hvm kexec: rebind virqs to existing eventchannel ports

During a kexec boot some virqs such as timer and debugirq were already
registered by the old kernel.  The hypervisor will return -EEXISTS from
the new EVTCHNOP_bind_virq request and the BUG in bind_virq_to_irq()
triggers.  Catch the -EEXISTS error and loop through all possible ports to find
what port belongs to the virq/cpu combo.

Signed-off-by: Olaf Hering <olaf@aepfle.de>
[v2:
  - use NR_EVENT_CHANNELS instead of private MAX_EVTCHNS]
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 32 insertions, 5 deletions

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 30df85d8fca8..31493e906bbd 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -877,11 +877,32 @@ static int bind_interdomain_evtchn_to_irq(unsigned int remote_domain,
         return err ? : bind_evtchn_to_irq(bind_interdomain.local_port);
 }
 
+static int find_virq(unsigned int virq, unsigned int cpu)
+{
+        struct evtchn_status status;
+        int port, rc = -ENOENT;
+
+        memset(&status, 0, sizeof(status));
+        for (port = 0; port <= NR_EVENT_CHANNELS; port++) {
+                status.dom = DOMID_SELF;
+                status.port = port;
+                rc = HYPERVISOR_event_channel_op(EVTCHNOP_status, &status);
+                if (rc < 0)
+                        continue;
+                if (status.status != EVTCHNSTAT_virq)
+                        continue;
+                if (status.u.virq == virq && status.vcpu == cpu) {
+                        rc = port;
+                        break;
+                }
+        }
+        return rc;
+}
 
 int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
 {
         struct evtchn_bind_virq bind_virq;
-        int evtchn, irq;
+        int evtchn, irq, ret;
 
         spin_lock(&irq_mapping_update_lock);
 
@@ -897,10 +918,16 @@ int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
 
                 bind_virq.virq = virq;
                 bind_virq.vcpu = cpu;
-                if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
-                                                &bind_virq) != 0)
-                        BUG();
-                evtchn = bind_virq.port;
+                ret = HYPERVISOR_event_channel_op(EVTCHNOP_bind_virq,
+                                                &bind_virq);
+                if (ret == 0)
+                        evtchn = bind_virq.port;
+                else {
+                        if (ret == -EEXIST)
+                                ret = find_virq(virq, cpu);
+                        BUG_ON(ret < 0);
+                        evtchn = ret;
+                }
 
                 xen_irq_info_virq_init(cpu, irq, evtchn, virq);