From: David Vrabel <david.vrabel@citrix.com>
Date: Thu, 15 Aug 2013 12:21:06 +0000 (+0100)
Subject: xen/events: initialize local per-cpu mask for all possible events
X-Git-Tag: firefly_0821_release~6453^2~981
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=d8251a942ff0318fd8fde8e69fac5480b60e26b3;p=firefly-linux-kernel-4.4.55.git

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@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index 6a6bbe4ede92..c7338868449a 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -346,7 +346,7 @@ 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)