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

Ian Campbell
2011-08-09T09:17:47Z

On Thu, 2011-08-04 at 17:20 +0100, Olaf Hering wrote:
> 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.

Would it be better to proactively just query the status of all event
channels early on, like you do in find_virq, and setup the irq info
structures as appropriate? Rather than waiting for an -EEXISTS I mean.

>
> Signed-off-by: Olaf Hering <olaf@aepfle.de>
>
> ---
> 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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