linux-kernel - Re: [PATCH 2/3] vfio/virqfd: Drain events from eventfd in virqfd

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Date:   Fri, 6 Nov 2020 16:29:56 -0700
From:   Alex Williamson <alex.williamson@...hat.com>
To:     David Woodhouse <dwmw2@...radead.org>,
        "Bonzini, Paolo" <pbonzini@...hat.com>
Cc:     Cornelia Huck <cohuck@...hat.com>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Jens Axboe <axboe@...nel.dk>, kvm@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH 2/3] vfio/virqfd: Drain events from eventfd in
 virqfd_wakeup()

On Tue, 27 Oct 2020 13:55:22 +0000
David Woodhouse <dwmw2@...radead.org> wrote:

> From: David Woodhouse <dwmw@...zon.co.uk>
> 
> Don't allow the events to accumulate in the eventfd counter, drain them
> as they are handled.
> 
> Signed-off-by: David Woodhouse <dwmw@...zon.co.uk>
> ---

Acked-by: Alex Williamson <alex.williamson@...hat.com>

Paolo, I assume you'll add this to your queue.  Thanks,

Alex

>  drivers/vfio/virqfd.c | 3 +++
>  1 file changed, 3 insertions(+)
> 
> diff --git a/drivers/vfio/virqfd.c b/drivers/vfio/virqfd.c
> index 997cb5d0a657..414e98d82b02 100644
> --- a/drivers/vfio/virqfd.c
> +++ b/drivers/vfio/virqfd.c
> @@ -46,6 +46,9 @@ static int virqfd_wakeup(wait_queue_entry_t *wait, unsigned mode, int sync, void
>  	__poll_t flags = key_to_poll(key);
>  
>  	if (flags & EPOLLIN) {
> +		u64 cnt;
> +		eventfd_ctx_do_read(virqfd->eventfd, &cnt);
> +
>  		/* An event has been signaled, call function */
>  		if ((!virqfd->handler ||
>  		     virqfd->handler(virqfd->opaque, virqfd->data)) &&