On 15/07/14 14:40, Vitaly Kuznetsov wrote:
> When kexec is being run PIRQs from Qemu-emulated devices are still
> mapped to old event channels and new kernel has no information about
> that. Trying to map them twice results in the following in Xen's dmesg:
>
> (XEN) irq.c:2278: dom7: pirq 24 or emuirq 8 already mapped
> (XEN) irq.c:2278: dom7: pirq 24 or emuirq 12 already mapped
> (XEN) irq.c:2278: dom7: pirq 24 or emuirq 1 already mapped
> ...
>
> and the following in new kernel's dmesg:
>
> [ 92.286796] xen:events: Failed to obtain physical IRQ 4
>
> The result is that the new kernel doesn't recieve IRQs for Qemu-emulated
> devices. Address the issue by unmapping all mapped PIRQs on kernel shutdown
> when kexec was requested and on every kernel startup. We need to do this
> twice to deal with the following issues:
> - startup-time unmapping is required to make kdump work;
> - shutdown-time unmapping is required to support kexec-ing non-fixed kernels;
> - shutdown-time unmapping is required to make Qemu-emulated NICs work after
> kexec (event channel is being closed on shutdown but no PHYSDEVOP_unmap_pirq
> is being performed).
I think this should be done only in one place -- just prior to exec'ing
the new kernel (including kdump kernels).
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -768,6 +768,7 @@ void xen_kexec_shutdown(void)
> #ifdef CONFIG_KEXEC
> if (!kexec_in_progress)
> return;
> + xen_unmap_all_pirqs();
> #endif
> }
>
> diff --git a/drivers/xen/events/events_base.c
> b/drivers/xen/events/events_base.c
> index c919d3d..7701c7f 100644
> --- a/drivers/xen/events/events_base.c
> +++ b/drivers/xen/events/events_base.c
> @@ -1643,6 +1643,80 @@ void xen_callback_vector(void) {}
> static bool fifo_events = true;
> module_param(fifo_events, bool, 0);
>
> +void xen_unmap_all_pirqs(void)
> +{
> + int pirq, rc, gsi, irq, evtchn;
> + struct physdev_unmap_pirq unmap_irq;
> + struct irq_info *info;
> + struct evtchn_close close;
> +
> + mutex_lock(&irq_mapping_update_lock);
> +
> + list_for_each_entry(info, &xen_irq_list_head, list) {
> + if (info->type != IRQT_PIRQ)
> + continue;
I think you need to do this by querying Xen state rather than relying on
potentially bad guest state. Particularly since you may crash while
holding irq_mapping_update_lock.
EVTCHNOP_status gets you the info you need I think.
David
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