linux/drivers/xen/events
Boris Ostrovsky ff1e22e7a6 xen/events: Mask a moving irq
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>
Cc: stable@vger.kernel.org
Signed-off-by: David Vrabel <david.vrabel@citrix.com>
2016-04-04 11:18:00 +01:00
..
events_2l.c xen: features and fixes for 4.6-rc0 2016-03-22 12:55:17 -07:00
events_base.c xen/events: Mask a moving irq 2016-04-04 11:18:00 +01:00
events_fifo.c xen: audit usages of module.h ; remove unnecessary instances 2016-03-21 15:13:32 +00:00
events_internal.h Revert "xen/events/fifo: Handle linked events when closing a port" 2015-08-11 11:05:42 +01:00
Makefile xen/events: use the FIFO-based ABI if available 2014-01-06 10:07:57 -05:00