From: Borislav Petkov <bp@alien8.de>
To: "Rafael J. Wysocki" <rjw@rjwysocki.net>
Cc: x86 <x86@kernel.org>, LKML <linux-kernel@vger.kernel.org>,
Len Brown <len.brown@intel.com>,
Linux PM <linux-pm@vger.kernel.org>,
Srinivas Pandruvada <srinivas.pandruvada@linux.intel.com>,
Laura Abbott <labbott@fedoraproject.org>,
Thomas Gleixner <tglx@linutronix.de>,
Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>,
Simon Schricker <sschricker@suse.de>,
Hannes Reinecke <hare@suse.de>
Subject: Re: [PATCH 1/2] PM / arch: x86: Rework the MSR_IA32_ENERGY_PERF_BIAS handling
Date: Fri, 22 Mar 2019 15:28:28 +0100 [thread overview]
Message-ID: <20190322142828.GA12472@zn.tnic> (raw)
In-Reply-To: <1605148.8jT99SsvVP@aspire.rjw.lan>
On Thu, Mar 21, 2019 at 11:18:01PM +0100, Rafael J. Wysocki wrote:
> From: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
>
> The current handling of MSR_IA32_ENERGY_PERF_BIAS in the kernel is
> problematic, because it may cause changes made by user space to that
> MSR (with the help of the x86_energy_perf_policy tool, for example)
One more reason to control MSR accesses from userspace. I'm working on
a series to even completely forbid accesses to some MSRs over /dev/msr
so I think accessing MSR_IA32_ENERGY_PERF_BIAS solely over the new
interface in patch 2 would be much better.
So, you're carrying those and you'd like to have an ACK from me?
Btw, a couple of nitpicks below.
> Index: linux-pm/arch/x86/kernel/cpu/intel_epb.c
> ===================================================================
> --- /dev/null
> +++ linux-pm/arch/x86/kernel/cpu/intel_epb.c
> @@ -0,0 +1,131 @@
> +// SPDX-License-Identifier: GPL-2.0
...
> +static DEFINE_PER_CPU(u8, saved_epb);
> +
> +#define EPB_MASK 0x0fULL
> +#define EPB_SAVED 0x10ULL
> +
> +static int intel_epb_save(void)
I'd drop that "intel_epb_" prefix from those static functions, but your
call...
> +{
> + u64 epb;
> +
> + rdmsrl(MSR_IA32_ENERGY_PERF_BIAS, epb);
> + /*
> + * Ensure that saved_epb will always be nonzero after this write even if
> + * the EPB value read from the MSR is 0.
> + */
> + this_cpu_write(saved_epb, (epb & EPB_MASK) | EPB_SAVED);
> +
> + return 0;
> +}
...
> Index: linux-pm/Documentation/admin-guide/pm/intel_epb.rst
> ===================================================================
> --- /dev/null
> +++ linux-pm/Documentation/admin-guide/pm/intel_epb.rst
WARNING: Missing or malformed SPDX-License-Identifier tag in line 1
#345: FILE: Documentation/admin-guide/pm/intel_epb.rst:1:
+======================================
> @@ -0,0 +1,6 @@
> +======================================
> +Intel Performance and Energy Bias Hint
> +======================================
> +
> +.. kernel-doc:: arch/x86/kernel/cpu/intel_epb.c
> + :doc: overview
> Index: linux-pm/Documentation/admin-guide/pm/working-state.rst
> ===================================================================
> --- linux-pm.orig/Documentation/admin-guide/pm/working-state.rst
> +++ linux-pm/Documentation/admin-guide/pm/working-state.rst
> @@ -8,3 +8,4 @@ Working-State Power Management
> cpuidle
> cpufreq
> intel_pstate
> + intel_epb
>
--
Regards/Gruss,
Boris.
Good mailing practices for 400: avoid top-posting and trim the reply.
next prev parent reply other threads:[~2019-03-22 14:28 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-21 22:12 [PATCH 0/2] PM / arch: x86: MSR_IA32_ENERGY_PERF_BIAS handling fixes and sysfs i/f Rafael J. Wysocki
2019-03-21 22:18 ` [PATCH 1/2] PM / arch: x86: Rework the MSR_IA32_ENERGY_PERF_BIAS handling Rafael J. Wysocki
2019-03-22 9:03 ` Hannes Reinecke
2019-03-22 14:28 ` Borislav Petkov [this message]
2019-03-22 14:31 ` Thomas Gleixner
2019-03-22 14:35 ` Borislav Petkov
2019-03-22 16:12 ` Thomas Gleixner
2019-03-22 16:52 ` Joe Perches
2019-03-25 10:06 ` Rafael J. Wysocki
2019-03-22 16:27 ` Thomas Renninger
2019-03-22 16:43 ` Borislav Petkov
2019-03-25 11:31 ` Borislav Petkov
2019-03-21 22:20 ` [PATCH 2/2] PM / arch: x86: MSR_IA32_ENERGY_PERF_BIAS sysfs interface Rafael J. Wysocki
2019-03-22 9:03 ` Hannes Reinecke
2019-03-22 14:46 ` Borislav Petkov
2019-03-25 10:01 ` Rafael J. Wysocki
2019-03-22 15:00 ` Peter Zijlstra
2019-03-25 9:56 ` Rafael J. Wysocki
2019-03-25 11:32 ` Borislav Petkov
2019-05-09 10:23 ` Ido Schimmel
2019-05-09 17:18 ` Rafael J. Wysocki
2019-05-09 17:43 ` Ido Schimmel
2019-05-09 21:28 ` [PATCH] x86: intel_epb: Take CONFIG_PM into account Rafael J. Wysocki
2019-05-10 6:01 ` Ingo Molnar
2019-05-27 10:56 ` [PATCH] x86: intel_epb: Do not build when CONFIG_PM is unset Rafael J. Wysocki
2019-05-30 7:47 ` Ingo Molnar
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