linux-kernel - Re: [PATCH 1/1] Add a new sysctl to disable io

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Date:   Wed, 28 Jun 2023 11:59:56 -0400
From:   Jeff Moyer <jmoyer@...hat.com>
To:     Matteo Rizzo <matteorizzo@...gle.com>
Cc:     Ricardo Ribalda <ribalda@...omium.org>,
        Bart Van Assche <bvanassche@....org>,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
        io-uring@...r.kernel.org, jordyzomer@...gle.com, evn@...gle.com,
        poprdi@...gle.com, corbet@....net, axboe@...nel.dk,
        asml.silence@...il.com, akpm@...ux-foundation.org,
        keescook@...omium.org, rostedt@...dmis.org,
        dave.hansen@...ux.intel.com, chenhuacai@...nel.org, steve@....org,
        gpiccoli@...lia.com, ldufour@...ux.ibm.com
Subject: Re: [PATCH 1/1] Add a new sysctl to disable io_uring system-wide

Matteo Rizzo <matteorizzo@...gle.com> writes:

> On Wed, 28 Jun 2023 at 13:44, Ricardo Ribalda <ribalda@...omium.org> wrote:
>>
>> Have you considered that the new sysctl is "sticky like kexec_load_disabled.
>> When the user disables it there is no way to turn it back on until the
>> system is rebooted.
>
> Are you suggesting making this sysctl sticky? Are there any examples of how to
> implement a sticky sysctl that can take more than 2 values in case we want to
> add an intermediate level that still allows privileged processes to use
> io_uring? Also, what would be the use case? Preventing privileged processes
> from re-enabling io_uring?

See unprivileged_bpf_disabled for an example.  I can't speak to the use
case for a sticky value.

-Jeff