linux-kernel - Re: [PATCH v2 0/2] io_uring: add a CQ ring flag to enable/disable eventfd notification

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Message-ID: <5795fd28-ee65-e610-5472-d1493902f2cd@kernel.dk>
Date:   Fri, 15 May 2020 12:17:40 -0600
From:   Jens Axboe <axboe@...nel.dk>
To:     Stefano Garzarella <sgarzare@...hat.com>
Cc:     linux-kernel@...r.kernel.org,
        Alexander Viro <viro@...iv.linux.org.uk>,
        io-uring@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] io_uring: add a CQ ring flag to enable/disable
 eventfd notification

On 5/15/20 10:38 AM, Stefano Garzarella wrote:
> v1 -> v2:
>  - changed the flag name and behaviour from IORING_CQ_NEED_EVENT to
>    IORING_CQ_EVENTFD_DISABLED [Jens]
> 
> The first patch adds the new 'cq_flags' field for the CQ ring. It
> should be written by the application and read by the kernel.
> 
> The second patch adds a new IORING_CQ_EVENTFD_DISABLED flag that can be
> used by the application to disable/enable eventfd notifications.
> 
> This feature can be useful if the application are using eventfd to be
> notified when requests are completed, but they don't want a notification
> for every request.
> Of course the application can already remove the eventfd from the event
> loop, but as soon as it adds the eventfd again, it will be notified,
> even if it has already handled all the completed requests.
> 
> The most important use case is when the registered eventfd is used to
> notify a KVM guest through irqfd and we want a mechanism to
> enable/disable interrupts.

Thanks, applied.

-- 
Jens Axboe