From eabe741782d5a52ce884dba4bab8825f977ab1eb Mon Sep 17 00:00:00 2001
From: Juergen Gross <jgross@suse.com>
Date: Thu, 22 Oct 2020 11:49:06 +0200
Subject: [PATCH] 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>
---
drivers/xen/events/events_fifo.c | 3 +++
1 file changed, 3 insertions(+)
diff --git a/drivers/xen/events/events_fifo.c b/drivers/xen/events/events_fifo.c
index 243e7b6d7b965..b234f1766810c 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;
--
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