From: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
This patch has been added to the 3.12 stable tree. If you have any
objections, please let us know.
===============
commit ff1e22e7a638a0782f54f81a6c9cb139aca2da35 upstream.
Moving an unmasked irq may result in irq handler being invoked on both
source and target CPUs.
With 2-level this can happen as follows:
On source CPU:
evtchn_2l_handle_events() ->
generic_handle_irq() ->
handle_edge_irq() ->
eoi_pirq():
irq_move_irq(data);
/***** WE ARE HERE *****/
if (VALID_EVTCHN(evtchn))
clear_evtchn(evtchn);
If at this moment target processor is handling an unrelated event in
evtchn_2l_handle_events()'s loop it may pick up our event since target's
cpu_evtchn_mask claims that this event belongs to it *and* the event is
unmasked and still pending. At the same time, source CPU will continue
executing its own handle_edge_irq().
With FIFO interrupt the scenario is similar: irq_move_irq() may result
in a EVTCHNOP_unmask hypercall which, in turn, may make the event
pending on the target CPU.
We can avoid this situation by moving and clearing the event while
keeping event masked.
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: David Vrabel <david.vrabel@xxxxxxxxxx>
Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
---
drivers/xen/events.c | 28 ++++++++++++++++++++++++----
1 file changed, 24 insertions(+), 4 deletions(-)
diff --git a/drivers/xen/events.c b/drivers/xen/events.c
index bd12a6660fe3..3715a54117bb 100644
--- a/drivers/xen/events.c
+++ b/drivers/xen/events.c
@@ -573,9 +573,19 @@ static void eoi_pirq(struct irq_data *data)
struct physdev_eoi eoi = { .irq = pirq_from_irq(data->irq) };
int rc = 0;
- irq_move_irq(data);
+ if (!VALID_EVTCHN(evtchn))
+ return;
- if (VALID_EVTCHN(evtchn))
+ if (unlikely(irqd_is_setaffinity_pending(data))) {
+ int masked = test_and_set_mask(evtchn);
+
+ clear_evtchn(evtchn);
+
+ irq_move_masked_irq(data);
+
+ if (!masked)
+ unmask_evtchn(evtchn);
+ } else
clear_evtchn(evtchn);
if (pirq_needs_eoi(data->irq)) {
@@ -1603,9 +1613,19 @@ static void ack_dynirq(struct irq_data *data)
{
int evtchn = evtchn_from_irq(data->irq);
- irq_move_irq(data);
+ if (!VALID_EVTCHN(evtchn))
+ return;
- if (VALID_EVTCHN(evtchn))
+ if (unlikely(irqd_is_setaffinity_pending(data))) {
+ int masked = test_and_set_mask(evtchn);
+
+ clear_evtchn(evtchn);
+
+ irq_move_masked_irq(data);
+
+ if (!masked)
+ unmask_evtchn(evtchn);
+ } else
clear_evtchn(evtchn);
}
--
2.8.1
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