| From | Ben Hutchings <> | Date | Wed, 27 Apr 2016 01:02:24 +0200 | Subject | [PATCH 3.2 070/115] xen/events: Mask a moving irq |
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3.2.80-rc1 review patch. If anyone has any objections, please let me know.
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From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
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@oracle.com> Signed-off-by: David Vrabel <david.vrabel@citrix.com> [bwh: Backported to 3.2: - Adjust filename - Add a suitable definition of test_and_set_mask()] Signed-off-by: Ben Hutchings <ben@decadent.org.uk> --- --- a/drivers/xen/events.c +++ b/drivers/xen/events.c @@ -337,6 +337,12 @@ static inline int test_evtchn(int port) return sync_test_bit(port, &s->evtchn_pending[0]); } +static inline int test_and_set_mask(int port) +{ + struct shared_info *s = HYPERVISOR_shared_info; + return sync_test_and_set_bit(port, &s->evtchn_mask[0]); +} + /** * notify_remote_via_irq - send event to remote end of event channel via irq @@ -507,9 +513,19 @@ static void eoi_pirq(struct irq_data *da 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)) { @@ -1427,9 +1443,19 @@ static void ack_dynirq(struct irq_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); }
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