Re: [PATCH RFC 3/4] xen/pvhvm: Unmap all PIRQs on startup and shutdown

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

On Tue, Jul 15, 2014 at 03:40:39PM +0200, 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).

How does this work when you boot the guest under Xen 4.4 where the FIFO events
are used? Does it still work correctly?

Thanks.
> 
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
>  arch/x86/xen/smp.c               |  1 +
>  drivers/xen/events/events_base.c | 76 ++++++++++++++++++++++++++++++++++++++++
>  include/xen/events.h             |  3 ++
>  3 files changed, 80 insertions(+)
> 
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index 35dcf39..e2b4deb 100644
> --- 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;
> +
> +		pirq = info->u.pirq.pirq;
> +		gsi = info->u.pirq.gsi;
> +		evtchn = info->evtchn;
> +		irq = info->irq;
> +
> +		pr_debug("unmapping pirq gsi=%d pirq=%d irq=%d evtchn=%d\n",
> +			gsi, pirq, irq, evtchn);
> +
> +		if (evtchn > 0) {
> +			close.port = evtchn;
> +			if (HYPERVISOR_event_channel_op(EVTCHNOP_close,
> +							&close) != 0)
> +				pr_warn("close evtchn %d failed\n", evtchn);
> +		}
> +
> +		unmap_irq.pirq = pirq;
> +		unmap_irq.domid = DOMID_SELF;
> +
> +		rc = HYPERVISOR_physdev_op(PHYSDEVOP_unmap_pirq, &unmap_irq);
> +		if (rc)
> +			pr_warn("unmap pirq failed gsi=%d pirq=%d irq=%d rc=%d\n",
> +				gsi, pirq, irq, rc);
> +	}
> +
> +	mutex_unlock(&irq_mapping_update_lock);
> +}
> +EXPORT_SYMBOL_GPL(xen_unmap_all_pirqs);

Why the EXPORT? Is this used by modules?
> +
> +static void xen_startup_unmap_pirqs(void)
> +{
> +	struct evtchn_status status;
> +	int port, rc = -ENOENT;
> +	struct physdev_unmap_pirq unmap_irq;
> +	struct evtchn_close close;
> +
> +	memset(&status, 0, sizeof(status));
> +	for (port = 0; port < xen_evtchn_max_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_pirq) {
> +			close.port = port;
> +			if (HYPERVISOR_event_channel_op(EVTCHNOP_close,
> +							&close) != 0)
> +				pr_warn("xen: failed to close evtchn %d\n",
> +					port);
> +			unmap_irq.pirq = status.u.pirq;
> +			unmap_irq.domid = DOMID_SELF;
> +			pr_warn("xen: unmapping previously mapped pirq %d\n",
> +				unmap_irq.pirq);
> +			if (HYPERVISOR_physdev_op(PHYSDEVOP_unmap_pirq,
> +						  &unmap_irq) != 0)
> +				pr_warn("xen: failed to unmap pirq %d\n",
> +					unmap_irq.pirq);
> +		}
> +	}
> +}
> +
> +
>  void __init xen_init_IRQ(void)
>  {
>  	int ret = -EINVAL;
> @@ -1671,6 +1745,8 @@ void __init xen_init_IRQ(void)
>  		xen_callback_vector();
>  
>  	if (xen_hvm_domain()) {
> +		xen_startup_unmap_pirqs();
> +
>  		native_init_IRQ();
>  		/* pci_xen_hvm_init must be called after native_init_IRQ so that
>  		 * __acpi_register_gsi can point at the right function */
> diff --git a/include/xen/events.h b/include/xen/events.h
> index 8bee7a7..3f9f428 100644
> --- a/include/xen/events.h
> +++ b/include/xen/events.h
> @@ -122,6 +122,9 @@ int xen_irq_from_gsi(unsigned gsi);
>  /* Determine whether to ignore this IRQ if it is passed to a guest. */
>  int xen_test_irq_shared(int irq);
>  
> +/* Unmap all PIRQs and close event channels */
> +void xen_unmap_all_pirqs(void);
> +
>  /* initialize Xen IRQ subsystem */
>  void xen_init_IRQ(void);
>  #endif	/* _XEN_EVENTS_H */
> -- 
> 1.9.3
>