diff mbox series

[v2,4/5] xen/events: unmask a fifo event channel only if it was masked

Message ID 20201022094907.28560-5-jgross@suse.com (mailing list archive)
State Accepted
Commit eabe741782d5a52ce884dba4bab8825f977ab1eb
Headers show
Series xen: event handling cleanup | expand

Commit Message

Jürgen Groß Oct. 22, 2020, 9:49 a.m. UTC 
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>
---
V2:
- move test for already unmasked into loop (Jan Beulich)
---
 drivers/xen/events/events_fifo.c | 3 +++
 1 file changed, 3 insertions(+)
diff mbox series

Patch

diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c
index 243e7b6d7b96..b234f1766810 100644
--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -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;