[Xen-devel] [PATCH] irq: Exclude percpu IRQs from being fixed up

["Zhang, Fengzhe" <fengzhe.zhang@xxxxxxxxx>]

irq: Exclude percpu IRQs from being fixed up

Xen spin unlock uses spurious ipi "lock_kicker_irq" to wake up blocked vCPUs 
waiting on that lock. This irq should always be disabled. However, when Dom0 is 
shuting down, function fixup_irqs is called which unmasks all irqs. Function 
unmask_irq effectively re-enables lock_kicker_irq and its irq handler is 
invoked which reports bug and crashes Dom0.

This patch sets IRQ_PER_CPU flag in irq desc and excludes percpu IRQs from 
being fixed up when taking CPUs down.

Signed-off-by: Fengzhe Zhang <fengzhe.zhang@xxxxxxxxx>

diff --git a/arch/x86/kernel/irq_64.c b/arch/x86/kernel/irq_64.c
index 977d8b4..f0f9450 100644
--- a/arch/x86/kernel/irq_64.c
+++ b/arch/x86/kernel/irq_64.c
@@ -80,6 +80,9 @@ void fixup_irqs(void)
                if (irq == 2)
                        continue;
 
+               if (desc->status & IRQ_PER_CPU)
+                       continue;
+
                /* interrupt's are disabled at this point */
                spin_lock(&desc->lock);
 
diff --git a/kernel/irq/manage.c b/kernel/irq/manage.c
index f34e231..26bc55a 100644
--- a/kernel/irq/manage.c
+++ b/kernel/irq/manage.c
@@ -727,10 +727,9 @@ __setup_irq(unsigned int irq, struct irq_desc *desc, 
struct irqaction *new)
                                goto out_thread;
                } else
                        compat_irq_chip_set_default_handler(desc);
-#if defined(CONFIG_IRQ_PER_CPU)
+
                if (new->flags & IRQF_PERCPU)
                        desc->status |= IRQ_PER_CPU;
-#endif
 
                desc->status &= ~(IRQ_AUTODETECT | IRQ_WAITING | IRQ_ONESHOT |
                                  IRQ_INPROGRESS | IRQ_SPURIOUS_DISABLED);

Attachment: lock_kicker_irq_bug.patch
Description: lock_kicker_irq_bug.patch

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