Re: [PATCH, resend] replacement for noirqdebug hack

[Keir Fraser <Keir.Fraser@cl.cam.ac.uk>]

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On 2 Jun 2006, at 11:02, Jan Beulich wrote:

> Instead of re-establishing the noirqdebug hack earlier present in the 
> i386 Linux code, communicate the information about
> whether a particular IRQ is shared across domains from hypervisor to 
> kernel.
>
> Signed-off-by: Jan Beulich <jbeulich@novell.com>

How about the following patch, which is a cleaner modification to Linux 
and does not affect shared_info layout? Note that it depends on a Xen 
patch that is currently in the staging tree (extends the irq info 
hypercall to inform about sharing status), and that the patch is 
against xen-unstable. The status check is much slower than reading from 
shared memory, but ought to be on a rare path (unless you have a 
high-rate interrupt line shared across guests, which is going to be 
rather suckful anyway).

  -- Keir


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--- olinux-2.6.16.13/drivers/xen/Kconfig	Wed Jun  7 14:51:56 2006
+++ nlinux-2.6.16.13/drivers/xen/Kconfig	Wed Jun  7 16:11:05 2006
@@ -224,6 +224,10 @@
 	bool
 	default y
 
+config HAVE_IRQ_IGNORE_UNHANDLED
+	bool
+	default y
+
 config NO_IDLE_HZ
 	bool
 	default y
--- olinux-2.6.16.13/drivers/xen/core/evtchn.c	Wed Jun  7 14:51:56 2006
+++ nlinux-2.6,16.13/drivers/xen/core/evtchn.c	Wed Jun  7 16:11:05 2006
@@ -678,6 +678,13 @@
 	set_affinity_irq
 };
 
+int irq_ignore_unhandled(unsigned int irq)
+{
+	struct physdev_irq_status_query irq_status = { .irq = irq };
+	(void)HYPERVISOR_physdev_op(PHYSDEVOP_irq_status_query, &irq_status);
+	return !!(irq_status.flags & XENIRQSTAT_shared);
+}
+
 void resend_irq_on_evtchn(struct hw_interrupt_type *h, unsigned int i)
 {
 	int evtchn = evtchn_from_irq(i);
--- olinux-2.6.16.13/include/linux/interrupt.h	2006-05-02 22:38:44.000000000 +0100
+++ nlinux-2.6.16.13/include/linux/interrupt.h	2006-06-07 16:05:04.000000000 +0100
@@ -58,6 +58,12 @@
 extern void enable_irq(unsigned int irq);
 #endif
 
+#ifdef CONFIG_HAVE_IRQ_IGNORE_UNHANDLED
+int irq_ignore_unhandled(unsigned int irq);
+#else
+#define irq_ignore_unhandled(irq) 0
+#endif
+
 #ifndef __ARCH_SET_SOFTIRQ_PENDING
 #define set_softirq_pending(x) (local_softirq_pending() = (x))
 #define or_softirq_pending(x)  (local_softirq_pending() |= (x))
--- olinux-2.6.16.13/kernel/irq/spurious.c	2006-05-02 22:38:44.000000000 +0100
+++ nlinux-2.6.16.13/kernel/irq/spurious.c	2006-06-07 16:01:39.000000000 +0100
@@ -137,7 +137,8 @@
 			struct pt_regs *regs)
 {
 	if (action_ret != IRQ_HANDLED) {
-		desc->irqs_unhandled++;
+		if (!irq_ignore_unhandled(irq))
+			desc->irqs_unhandled++;
 		if (action_ret != IRQ_NONE)
 			report_bad_irq(irq, desc, action_ret);
 	}

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