linux-kernel - [PATCH 4.0 025/148] xen/events: dont bind non-percpu VIRQs with percpu chip

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Date:	Wed,  3 Jun 2015 21:08:15 +0900
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, David Vrabel <david.vrabel@...rix.com>
Subject: [PATCH 4.0 025/148] xen/events: dont bind non-percpu VIRQs with percpu chip

4.0-stable 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>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>

---
 drivers/tty/hvc/hvc_xen.c        |    2 +-
 drivers/xen/events/events_base.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
@@ -289,7 +289,7 @@ static int xen_initial_domain_console_in
 			return -ENOMEM;
 	}
 
-	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0);
+	info->irq = bind_virq_to_irq(VIRQ_CONSOLE, 0, false);
 	info->vtermno = HVC_COOKIE;
 
 	spin_lock(&xencons_lock);
--- a/drivers/xen/events/events_base.c
+++ b/drivers/xen/events/events_base.c
@@ -957,7 +957,7 @@ unsigned xen_evtchn_nr_channels(void)
 }
 EXPORT_SYMBOL_GPL(xen_evtchn_nr_channels);
 
-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;
@@ -971,8 +971,12 @@ int bind_virq_to_irq(unsigned int virq,
 		if (irq < 0)
 			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;
@@ -1062,7 +1066,7 @@ 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
@@ -17,7 +17,7 @@ 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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