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

[Vitaly Kuznetsov <vkuznets@redhat.com>]

Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> writes:

> 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 for pointing that out! I've checked and it doesn't. However
patches make no difference - guest kernel gets stuck on boot with and
without them. Will try to investigate...

>
> 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
>> 

-- 
  Vitaly