linux-kernel - Re: [PATCH RFC] intel_pstate: play well with frequency limits set by acpi

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

Message-ID: <1437493051.2377.170.camel@spandruv-DESK3.jf.intel.com>
Date:	Tue, 21 Jul 2015 08:37:31 -0700
From:	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>
To:	Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
Cc:	Konstantin Khlebnikov <koct9i@...il.com>, linux-pm@...r.kernel.org,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	linux-acpi@...r.kernel.org,
	Kristen Carlson Accardi <kristen@...ux.intel.com>,
	Len Brown <lenb@...nel.org>, Ethan Zhao <ethan.zhao@...cle.com>
Subject: Re: [PATCH RFC] intel_pstate: play well with frequency limits set
 by acpi

On Tue, 2015-07-21 at 13:25 +0300, Konstantin Khlebnikov wrote:
> On 21.07.2015 00:08, Srinivas Pandruvada wrote:
> > On Fri, 2015-07-17 at 07:36 +0300, Konstantin Khlebnikov wrote:
> >> On Fri, Jul 17, 2015 at 1:08 AM, Srinivas Pandruvada
> >> <srinivas.pandruvada@...ux.intel.com> wrote:
> >>> On Thu, 2015-07-16 at 21:17 +0300, Konstantin Khlebnikov wrote:
> >>>> IPMI can control CPU P-states remotely: configuration is reported via
> >>>> common ACPI interface (_PPC/_PSS/etc). This patch adds required minimal
> >>>> support in intel_pstate to receive and use these P-state limits.
> >>>>
> >>>> * ignore limit of top state in _PPC: it lower than turbo boost frequency
> >>>> * register intel_pstate in acpi-processor to get states from _PSS
> >>>> * link acpi_processor_get_bios_limit: this adds attribute "bios_limit"
> >>>>
> >>>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
> >>>> ---
> >>>>   drivers/acpi/processor_perflib.c |    3 +-
> >>>>   drivers/cpufreq/intel_pstate.c   |   57 ++++++++++++++++++++++++++++++++++++++
> >>>>   2 files changed, 59 insertions(+), 1 deletion(-)
> >>>>
> >>>> diff --git a/drivers/acpi/processor_perflib.c b/drivers/acpi/processor_perflib.c
> >>>> index cfc8aba72f86..781e328c9d5f 100644
> >>>> --- a/drivers/acpi/processor_perflib.c
> >>>> +++ b/drivers/acpi/processor_perflib.c
> >>>> @@ -98,7 +98,8 @@ static int acpi_processor_ppc_notifier(struct notifier_block *nb,
> >>>>
> >>>>        ppc = (unsigned int)pr->performance_platform_limit;
> >>>>
> >>>> -     if (ppc >= pr->performance->state_count)
> >>>> +     /* Ignore limit of top state: it lower than turbo boost frequency */
> >>>> +     if (!ppc || ppc >= pr->performance->state_count)
> >>> Why? Isn't the previous check enough?
> >>
> >> Zero _PPC state must be top performance state but as I see frequency in
> >> _PSS is lower than maximum possible turbo frequency. So, in this case
> >> intel_pstate cannnot get "100%"  for max bound even it there is no limit set.
> >>
> >> For example: I saw _PSS[0] = 2601 Mhz, PSS[1] = 2600 Mhz while turbo
> >> state is 3400 Mhz.
> >>
> > Have you tested dynamic _PPC modification with acpi cpufreq with this
> > change (after boot)? Suppose _PPC is changed from 3 to 0, then
> > cpufreq_verify_within_limits will not be called to change to new max
> > turbo performance state.
> >
> 
> I haven't checked that but as I see acpi_processor_ppc_notifier()
> can only reduce maximum frequency. So, there should be no problem
> in this case.
No, it can also be used in both ways. Once reduced, it can increase as
well. _PPC can be dynamically modified by BIOS to reduce and also to
increase.



--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/