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xen/events: unmask a fifo event channel only if it was masked 

Unmasking an event channel with fifo events channels being used can
require a hypercall to be made, so try to avoid that by checking
whether the event channel was really masked.

Suggested-by: Jan Beulich <jbeulich@suse.com>
Signed-off-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Link: https://lore.kernel.org/r/20201022094907.28560-5-jgross@suse.com
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
zero-sugar-mainline-defconfig
Juergen Gross 2020-10-22 11:49:06 +02:00 committed by Boris Ostrovsky
parent d04b1ae5a9
commit eabe741782
1 changed files with 3 additions and 0 deletions
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3
drivers/xen/events/events_fifo.c
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@ -237,6 +237,9 @@ static bool clear_masked_cond(volatile event_word_t *word)
w = *word;
do {
if (!(w & (1 << EVTCHN_FIFO_MASKED)))
return true;
if (w & (1 << EVTCHN_FIFO_PENDING))
return false;