Re: [PATCH 0/3] idle, Honor Hardware Disabled States

From: Prarit Bhargava
Date: Wed Mar 23 2016 - 19:50:58 EST




On 03/23/2016 04:05 PM, Len Brown wrote:
> This patch assumes that if a package state is disabled,
> the corresponding core state must be disabled.
> That assumption is false.
> Indeed, that is a very popular and useful configuration.
>
> But even if that were not the case, this software is not necessary,
> since the hardware handles demotion "c-state clipping" automatically.
>
> Yes, there is a case where a certain version of a certain processor
> has broken demotion, but this isn't the right fix for that.
> The right fix for that is here:
>
> https://bugzilla.kernel.org/show_bug.cgi?id=109081

Len, should I rebase on top of this? Would that work for you?

P.

>
> and will be upstream shortly.
>
> thanks,
> -Len
>
>
>
> On Mon, Mar 21, 2016 at 8:49 AM, Prarit Bhargava <prarit@xxxxxxxxxx> wrote:
>> Some Intel processors have cstates limited by MSR_PKG_CST_CONFIG_CONTROL
>> (0xE2), which specifies the lowest processor-specific C-state code name
>> (consuming the least power). The intel_idle driver does not query this MSR to
>> see if states are limited by hardware. In the case of the i7-6700HQ the value
>> of bits 3:0 on the MSR are 0x6, meaning that C9-SKL (0x7) and C10-SKL (0x8)
>> should have been disabled.
>>
>> This patch adds a limit field to the cpuidle_state struct to hold the
>> cstate encodings for each processor, and queries the values the values
>> to confirm support.
>>
>> After applying this patchset the system now boots and reports that
>> some states have been disabled:
>>
>> [root@dhcp40-125 ~]# dmesg | grep intel_idle
>> [ 1.163367] intel_idle: MWAIT substates: 0x11142120
>> [ 1.163368] intel_idle: v0.4 model 0x5E
>> [ 1.163369] intel_idle: lapic_timer_reliable_states 0xffffffff
>> [ 1.163370] intel_idle: state C9-SKL (0x7) is disabled. Max Package limit is 0x6.
>> [ 1.163371] intel_idle: state C10-SKL (0x8) is disabled. Max Package limit is 0x6.
>>
>> Cc: x86@xxxxxxxxxx
>> Cc: Len Brown <lenb@xxxxxxxxxx>
>> Cc: "Peter Zijlstra (Intel)" <peterz@xxxxxxxxxxxxx>
>> Cc: Borislav Petkov <bp@xxxxxxx>
>> Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
>> Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
>> Cc: Dasaratharaman Chandramouli <dasaratharaman.chandramouli@xxxxxxxxx>
>> Cc: linux-pm@xxxxxxxxxxxxxxx
>> Signed-off-by: Prarit Bhargava <prarit@xxxxxxxxxx>
>>
>> Prarit Bhargava (3):
>> idle, rename MSR_NHM_SNB_PKG_CST_CFG_CTL to
>> MSR_PKG_CST_CONFIG_CONTROL
>> intel_idle, Introduce cstate limits and fix hardware cstate disable
>> value
>> cpuidle, Prevent users from enabling cstates that are disabled in
>> Hardware
>>
>> arch/x86/include/asm/msr-index.h | 2 +-
>> drivers/cpuidle/governors/ladder.c | 3 ++
>> drivers/cpuidle/governors/menu.c | 4 ++
>> drivers/cpuidle/sysfs.c | 34 +++++++++++-
>> drivers/idle/intel_idle.c | 93 ++++++++++++++++++++++++++++++++-
>> include/linux/cpuidle.h | 11 +++-
>> tools/power/x86/turbostat/turbostat.8 | 2 +-
>> tools/power/x86/turbostat/turbostat.c | 10 ++--
>> 8 files changed, 146 insertions(+), 13 deletions(-)
>>
>> --
>> 1.7.9.3
>>
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