[Xen-devel] [PATCH 3/4] xen/events: initialize local per-cpu mask for all possible events

[David Vrabel <david.vrabel@xxxxxxxxxx>]

From: David Vrabel <david.vrabel@xxxxxxxxxx>

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@xxxxxxxxxx>
---
 drivers/xen/events.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index f866f50..fb88e32 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -348,7 +348,7 @@ 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)
-- 
1.7.2.5


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