[Xen-devel] [PATCH 2/3] xen/pv-on-hvm kexec: rebind virqs to existing eventchannel ports

[Olaf Hering <olaf@xxxxxxxxx>]

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@xxxxxxxxx>

---
 drivers/xen/events.c |   40 +++++++++++++++++++++++++++++++++++-----
 1 file changed, 35 insertions(+), 5 deletions(-)

Index: linux-3.0/drivers/xen/events.c
===================================================================
--- linux-3.0.orig/drivers/xen/events.c
+++ linux-3.0/drivers/xen/events.c
@@ -877,11 +877,35 @@ static int bind_interdomain_evtchn_to_ir
        return err ? : bind_evtchn_to_irq(bind_interdomain.local_port);
 }
 
+/* BITS_PER_LONG is used in Xen */
+#define MAX_EVTCHNS (64 * 64)
+
+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 <= MAX_EVTCHNS; 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 +921,16 @@ int bind_virq_to_irq(unsigned int virq,
 
                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);
 


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