linux-kernel - [PATCH 3.2 098/164] xen/events: don't bind non-percpu VIRQs with percpu chip

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Message-ID: <lsq.1438473757.549883071@decadent.org.uk>
Date:	Sun, 02 Aug 2015 01:02:37 +0100
From:	Ben Hutchings <ben@...adent.org.uk>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:	akpm@...ux-foundation.org, "David Vrabel" <david.vrabel@...rix.com>
Subject: [PATCH 3.2 098/164] xen/events: don't bind non-percpu VIRQs with
 percpu chip

3.2.70-rc1 review patch.  If anyone has any objections, please let me know.

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

From: David Vrabel <david.vrabel@...rix.com>

commit 77bb3dfdc0d554befad58fdefbc41be5bc3ed38a upstream.

A non-percpu VIRQ (e.g., VIRQ_CONSOLE) may be freed on a different
VCPU than it is bound to.  This can result in a race between
handle_percpu_irq() and removing the action in __free_irq() because
handle_percpu_irq() does not take desc->lock.  The interrupt handler
sees a NULL action and oopses.

Only use the percpu chip/handler for per-CPU VIRQs (like VIRQ_TIMER).

  # cat /proc/interrupts | grep virq
   40:      87246          0  xen-percpu-virq      timer0
   44:          0          0  xen-percpu-virq      debug0
   47:          0      20995  xen-percpu-virq      timer1
   51:          0          0  xen-percpu-virq      debug1
   69:          0          0   xen-dyn-virq      xen-pcpu
   74:          0          0   xen-dyn-virq      mce
   75:         29          0   xen-dyn-virq      hvc_console

Signed-off-by: David Vrabel <david.vrabel@...rix.com>
[bwh: Backported to 3.2: adjust filename, context, indentation]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/tty/hvc/hvc_xen.c |  2 +-
 drivers/xen/events.c      | 12 ++++++++----
 include/xen/events.h      |  2 +-
 3 files changed, 10 insertions(+), 6 deletions(-)

--- a/drivers/tty/hvc/hvc_xen.c
+++ b/drivers/tty/hvc/hvc_xen.c
@@ -167,7 +167,7 @@ static int __init xen_hvc_init(void)
 
 	if (xen_initial_domain()) {
 		ops = &dom0_hvc_ops;
-		xencons_irq = bind_virq_to_irq(VIRQ_CONSOLE, 0);
+		xencons_irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
 	} else {
 		if (!xen_start_info->console.domU.evtchn)
 			return -ENODEV;
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -895,7 +895,7 @@ static int find_virq(unsigned int virq,
 	return rc;
 }
 
-int bind_virq_to_irq(unsigned int virq, unsigned int cpu)
+int bind_virq_to_irq(unsigned int virq, unsigned int cpu, bool percpu)
 {
 	struct evtchn_bind_virq bind_virq;
 	int evtchn, irq, ret;
@@ -909,8 +909,12 @@ int bind_virq_to_irq(unsigned int virq,
 		if (irq == -1)
 			goto out;
 
-		irq_set_chip_and_handler_name(irq, &xen_percpu_chip,
-					      handle_percpu_irq, "virq");
+		if (percpu)
+			irq_set_chip_and_handler_name(irq, &xen_percpu_chip,
+						      handle_percpu_irq, "virq");
+		else
+			irq_set_chip_and_handler_name(irq, &xen_dynamic_chip,
+						      handle_edge_irq, "virq");
 
 		bind_virq.virq = virq;
 		bind_virq.vcpu = cpu;
@@ -1023,7 +1027,7 @@ int bind_virq_to_irqhandler(unsigned int
 {
 	int irq, retval;
 
-	irq = bind_virq_to_irq(virq, cpu);
+	irq = bind_virq_to_irq(virq, cpu, irqflags & IRQF_PERCPU);
 	if (irq < 0)
 		return irq;
 	retval = request_irq(irq, handler, irqflags, devname, dev_id);
--- a/include/xen/events.h
+++ b/include/xen/events.h
@@ -12,7 +12,7 @@ int bind_evtchn_to_irqhandler(unsigned i
 			      irq_handler_t handler,
 			      unsigned long irqflags, const char *devname,
 			      void *dev_id);
-int bind_virq_to_irq(unsigned int virq, unsigned int cpu);
+int bind_virq_to_irq(unsigned int virq, unsigned int cpu, bool percpu);
 int bind_virq_to_irqhandler(unsigned int virq, unsigned int cpu,
 			    irq_handler_t handler,
 			    unsigned long irqflags, const char *devname,

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