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    Subject[PATCH 43/58] xen/events: initialize local per-cpu mask for all possible events
    Date
    3.5.7.21 -stable review patch.  If anyone has any objections, please let me know.

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

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

    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: Luis Henriques <luis.henriques@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


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