linux-kernel - Re: [PATCH] ACPI: processor: Add QoS requests for all CPUs

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-ID: <20191025085132.qk6iynyavgvp7wlm@vireshk-i7>
Date:   Fri, 25 Oct 2019 14:21:32 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     "Rafael J. Wysocki" <rafael@...nel.org>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux ACPI <linux-acpi@...r.kernel.org>,
        Linux PM <linux-pm@...r.kernel.org>,
        Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] ACPI: processor: Add QoS requests for all CPUs

On 25-10-19, 10:17, Rafael J. Wysocki wrote:
> On Fri, Oct 25, 2019 at 4:53 AM Viresh Kumar <viresh.kumar@...aro.org> wrote:
> >
> > On 25-10-19, 02:41, Rafael J. Wysocki wrote:
> > > From: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> > >
> > > The _PPC change notifications from the platform firmware are per-CPU,
> > > so acpi_processor_ppc_init() needs to add a frequency QoS request
> > > for each CPU covered by a cpufreq policy to take all of them into
> > > account.
> > >
> > > Even though ACPI thermal control of CPUs sets frequency limits
> > > per processor package, it also needs a frequency QoS request for each
> > > CPU in a cpufreq policy in case some of them are taken offline and
> > > the frequency limit needs to be set through the remaining online
> > > ones (this is slightly excessive, because all CPUs covered by one
> > > cpufreq policy will set the same frequency limit through their QoS
> > > requests, but it is not incorrect).
> > >
> > > Modify the code in accordance with the above observations.
> >
> > I am not sure if I understood everything you just said, but I don't
> > see how things can break with the current code we have.
> >
> > Both acpi_thermal_cpufreq_init() and acpi_processor_ppc_init() are
> > called from acpi_processor_notifier() which is registered as a policy
> > notifier and is called when a policy is created or removed. Even if
> > some CPUs of a policy go offline, it won't matter as the request for
> > the policy stays and it will be dropped only when all the CPUs of a
> > policy go offline.
> >
> > What am I missing ?
> 
> The way the request is used.

Yes, I missed the point :)

-- 
viresh