linux-kernel - Re: [PATCH v3 01/14] sched/core: uclamp: extend sched

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Message-ID: <20180817111429.3nhqm3lrr42lzqho@queper01-lin>
Date:   Fri, 17 Aug 2018 12:14:31 +0100
From:   Quentin Perret <quentin.perret@....com>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     Juri Lelli <juri.lelli@...hat.com>, linux-kernel@...r.kernel.org,
        linux-pm@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Tejun Heo <tj@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v3 01/14] sched/core: uclamp: extend sched_setattr to
 support utilization clamping

On Friday 17 Aug 2018 at 11:57:31 (+0100), Patrick Bellasi wrote:
> On 17-Aug 11:34, Quentin Perret wrote:
> > Hi Patrick,
> > 
> > On Thursday 09 Aug 2018 at 16:23:13 (+0100), Patrick Bellasi wrote:
> > > On 09-Aug 11:50, Juri Lelli wrote:
> > > > On 09/08/18 10:14, Patrick Bellasi wrote:
> > > > > On 07-Aug 14:35, Juri Lelli wrote:
> > > > > > On 06/08/18 17:39, Patrick Bellasi wrote:
> > > 
> > > [...]
> > > 
> > > > > 1) make CAP_SYS_NICE protected the clamp groups, with an optional boot
> > > > >    time parameter to relax this check
> > > > 
> > > > It seems to me that this might work well with that the intended usage of
> > > > the interface that you depict above. SMS only (or any privileged user)
> > > > will be in control of how groups are configured, so no problem for
> > > > normal users.
> > > 
> > > Yes, well... apart normal users still getting a -ENOSPC is they are
> > > requesting one of the not pre-configured clamp values. Which is why
> > > the following bits can be helpful.
> > 
> > So IIUC, normal users would still be free of choosing their clamp values
> > as long as they choose one in the list of pre-allocated ones ? Is that
> > correct ?
> 
> No, with the CAP_SYS_NICE/ADMIN guard in place, as discussed above in
> point 1, the syscall will just fail for normal users.

Right, I just misunderstood then :-)
Sorry for the noise ...

Thanks,
Quentin