Re: [XEN PATCH] evtchn/fifo: Don't set PENDING bit if guest misbehaves

[Andrew Cooper <amc96@xxxxxxxx>]

On 16/03/2022 18:38, Raphael Ning wrote:
> From: Raphael Ning <raphning@xxxxxxxxxx>
>
> Currently, evtchn_fifo_set_pending() will mark the event as PENDING even
> if it fails to lock the FIFO event queue(s), or if the guest has not
> initialized the FIFO control block for the target vCPU. A well-behaved
> guest should never trigger either of these cases.
>
> There is no good reason to set the PENDING bit (the guest should not
> depend on this behaviour anyway) or check for pollers in such corner
> cases, so skip that. In fact, both the comment above the for loop and
> the commit message for
>
>  41a822c39263 xen/events: rework fifo queue locking
>
> suggest that the bit should be set after the FIFO queue(s) are locked.
>
> Take the opportunity to rename the was_pending variable (flipping its
> sense) and switch to the standard bool type.
>
> Suggested-by: David Vrabel <dvrabel@xxxxxxxxxxxx>
> Signed-off-by: Raphael Ning <raphning@xxxxxxxxxx>
> ---
>  xen/common/event_fifo.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
>
> diff --git a/xen/common/event_fifo.c b/xen/common/event_fifo.c
> index ed4d3beb10f3..6c74ccebebb7 100644
> --- a/xen/common/event_fifo.c
> +++ b/xen/common/event_fifo.c
> @@ -165,7 +165,7 @@ static void cf_check evtchn_fifo_set_pending(
>      unsigned int port;
>      event_word_t *word;
>      unsigned long flags;
> -    bool_t was_pending;
> +    bool_t check_pollers = false;

Considering your commit message, did you intend to change this to bool?

Can be fixed on commit.  Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

~Andrew

P.S. David - do you want your maintainership back?  None of this code
has undergone any major changes since you wrote it.