linux-kernel - [004/129] xen: use percpu interrupts for IPIs and VIRQs

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Date:	Sat, 18 Sep 2010 12:11:42 -0700
From:	Greg KH <gregkh@...e.de>
To:	linux-kernel@...r.kernel.org, stable@...nel.org
Cc:	stable-review@...nel.org, torvalds@...ux-foundation.org,
	akpm@...ux-foundation.org, alan@...rguk.ukuu.org.uk,
	Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Subject: [004/129] xen: use percpu interrupts for IPIs and VIRQs

2.6.35-stable review patch.  If anyone has any objections, please let us know.

------------------

From: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>

commit aaca49642b92c8a57d3ca5029a5a94019c7af69f upstream.

IPIs and VIRQs are inherently per-cpu event types, so treat them as such:
 - use a specific percpu irq_chip implementation, and
 - handle them with handle_percpu_irq

This makes the path for delivering these interrupts more efficient
(no masking/unmasking, no locks), and it avoid problems with attempts
to migrate them.

Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@...rix.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@...e.de>

---
 drivers/xen/events.c |   19 +++++++++++++++----
 1 file changed, 15 insertions(+), 4 deletions(-)

--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -107,6 +107,7 @@ static inline unsigned long *cpu_evtchn_
 #define VALID_EVTCHN(chn)	((chn) != 0)
 
 static struct irq_chip xen_dynamic_chip;
+static struct irq_chip xen_percpu_chip;
 
 /* Constructor for packed IRQ information. */
 static struct irq_info mk_unbound_info(void)
@@ -389,8 +390,8 @@ static int bind_ipi_to_irq(unsigned int
 		if (irq < 0)
 			goto out;
 
-		set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
-					      handle_level_irq, "ipi");
+		set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
+					      handle_percpu_irq, "ipi");
 
 		bind_ipi.vcpu = cpu;
 		if (HYPERVISOR_event_channel_op(EVTCHNOP_bind_ipi,
@@ -430,8 +431,8 @@ static int bind_virq_to_irq(unsigned int
 
 		irq = find_unbound_irq();
 
-		set_irq_chip_and_handler_name(irq, &xen_dynamic_chip,
-					      handle_level_irq, "virq");
+		set_irq_chip_and_handler_name(irq, &xen_percpu_chip,
+					      handle_percpu_irq, "virq");
 
 		evtchn_to_irq[evtchn] = irq;
 		irq_info[irq] = mk_virq_info(evtchn, virq);
@@ -934,6 +935,16 @@ static struct irq_chip xen_dynamic_chip
 	.retrigger	= retrigger_dynirq,
 };
 
+static struct irq_chip en_percpu_chip __read_mostly = {
+	.name		= "xen-percpu",
+
+	.disable	= disable_dynirq,
+	.mask		= disable_dynirq,
+	.unmask		= enable_dynirq,
+
+	.ack		= ack_dynirq,
+};
+
 void __init xen_init_IRQ(void)
 {
 	int i;


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