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Message-ID: <87wqbdk5kp.fsf@vitty.brq.redhat.com>
Date: Wed, 16 Jul 2014 11:37:10 +0200
From: Vitaly Kuznetsov <vkuznets@...hat.com>
To: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc: xen-devel@...ts.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@...cle.com>,
David Vrabel <david.vrabel@...rix.com>,
Stefano Stabellini <stefano.stabellini@...citrix.com>,
Andrew Jones <drjones@...hat.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 3/4] xen/pvhvm: Unmap all PIRQs on startup and shutdown
Konrad Rzeszutek Wilk <konrad.wilk@...cle.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@...hat.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
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