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Message-ID: <20140716134501.GI19585@laptop.dumpdata.com>
Date: Wed, 16 Jul 2014 09:45:01 -0400
From: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To: Vitaly Kuznetsov <vkuznets@...hat.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
On Wed, Jul 16, 2014 at 11:37:10AM +0200, Vitaly Kuznetsov wrote:
> 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...
I think for FIFO events we can't do much right now - it would need some
new hypercalls to de-allocate or such.
But I was thinking that your code logic could just return out when
it detects that it is running with FIFO events (with a TODO comment)
- and also spit out some information to this effect?
Say: "Use xen.fifo=0 in your launching kernel"
(don't know the right name for the kernel in which you do 'kexec -e' in ?
Is that launching? Original? Bootstrap kernel?)
>
> >
> > 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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