[ 3.5.y.z extended stable ] Patch "xen/events: initialize local per-cpu mask for all possible" has been added to staging queue

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    xen/events: initialize local per-cpu mask for all possible

to the linux-3.5.y-queue branch of the 3.5.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.5.y-queue

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.5.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

------

>From 7542678de9bb26c7dc8de8776d93674c2e7f9fb4 Mon Sep 17 00:00:00 2001
From: David Vrabel <david.vrabel at citrix.com>
Date: Thu, 15 Aug 2013 13:21:06 +0100
Subject: [PATCH] xen/events: initialize local per-cpu mask for all possible
 events

commit 84ca7a8e45dafb49cd5ca90a343ba033e2885c17 upstream.

The sizeof() argument in init_evtchn_cpu_bindings() is incorrect
resulting in only the first 64 (or 32 in 32-bit guests) ports having
their bindings being initialized to VCPU 0.

In most cases this does not cause a problem as request_irq() will set
the irq affinity which will set the correct local per-cpu mask.
However, if the request_irq() is called on a VCPU other than 0, there
is a window between the unmasking of the event and the affinity being
set were an event may be lost because it is not locally unmasked on
any VCPU. If request_irq() is called on VCPU 0 then local irqs are
disabled during the window and the race does not occur.

Fix this by initializing all NR_EVENT_CHANNEL bits in the local
per-cpu masks.

Signed-off-by: David Vrabel <david.vrabel at citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk at oracle.com>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 drivers/xen/events.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index b5b559a..025e98b 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -324,7 +324,7 @@ static void init_evtchn_cpu_bindings(void)

 	for_each_possible_cpu(i)
 		memset(per_cpu(cpu_evtchn_mask, i),
-		       (i == 0) ? ~0 : 0, sizeof(*per_cpu(cpu_evtchn_mask, i)));
+		       (i == 0) ? ~0 : 0, NR_EVENT_CHANNELS/8);
 }

 static inline void clear_evtchn(int port)
--
1.8.3.2