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

2020-10-22 Thread Jürgen Groß 

On 22.10.20 09:55, Jan Beulich wrote:

On 22.10.2020 09:42, Juergen Gross wrote:

--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -236,6 +236,9 @@ static bool clear_masked_cond(volatile event_word_t *word)
  
  	w = *word;
  
+	if (!(w & (1 << EVTCHN_FIFO_MASKED)))

+   return true;


Maybe better move this ...


do {
if (w & (1 << EVTCHN_FIFO_PENDING))
return false;



... into the loop, above this check?


Yes, that should be better.


Juergen

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

2020-10-22 Thread Jan Beulich 
On 22.10.2020 09:42, Juergen Gross wrote:
> --- a/drivers/xen/events/events_fifo.c
> +++ b/drivers/xen/events/events_fifo.c
> @@ -236,6 +236,9 @@ static bool clear_masked_cond(volatile event_word_t *word)
>  
>   w = *word;
>  
> + if (!(w & (1 << EVTCHN_FIFO_MASKED)))
> + return true;

Maybe better move this ...

>   do {
>   if (w & (1 << EVTCHN_FIFO_PENDING))
>   return false;
> 

... into the loop, above this check?

Jan

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

2020-10-22 Thread Juergen Gross 
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 
Signed-off-by: Juergen Gross 
---
 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 243e7b6d7b96..f60c5a9ec833 100644
--- a/drivers/xen/events/events_fifo.c
+++ b/drivers/xen/events/events_fifo.c
@@ -236,6 +236,9 @@ static bool clear_masked_cond(volatile event_word_t *word)
 
w = *word;
 
+   if (!(w & (1 << EVTCHN_FIFO_MASKED)))
+   return true;
+
do {
if (w & (1 << EVTCHN_FIFO_PENDING))
return false;
-- 
2.26.2