linux-kernel - Re: [PATCH v2 0/3] powernv/cpuidle: Fastsleep workaround and fixes

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Date:	Thu, 02 Oct 2014 22:10:47 +0530
From:	Shreyas B Prabhu <shreyas@...ux.vnet.ibm.com>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
CC:	linux-kernel@...r.kernel.org,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	linux-pm@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	"Srivatsa S. Bhat" <srivatsa@....edu>,
	"Preeti U. Murthy" <preeti@...ux.vnet.ibm.com>,
	Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
Subject: Re: [PATCH v2 0/3] powernv/cpuidle: Fastsleep workaround and fixes



On Thursday 02 October 2014 02:16 AM, Rafael J. Wysocki wrote:
> On Wednesday, October 01, 2014 01:15:57 PM Shreyas B. Prabhu wrote:
>> Fast sleep is an idle state, where the core and the L1 and L2
>> caches are brought down to a threshold voltage. This also means that
>> the communication between L2 and L3 caches have to be fenced. However
>> the current P8 chips have a bug wherein this fencing between L2 and
>> L3 caches get delayed by a cpu cycle. This can delay L3 response to
>> the other cpus if they request for data during this time. Thus they
>> would fetch the same data from the memory which could lead to data
>> corruption if L3 cache is not flushed. 
>>
>> This series overcomes above problem in kernel.
>>
>> Cc: Benjamin Herrenschmidt <benh@...nel.crashing.org>
>> Cc: Paul Mackerras <paulus@...ba.org>
>> Cc: Michael Ellerman <mpe@...erman.id.au>
>> Cc: Rafael J. Wysocki <rjw@...ysocki.net>
>> Cc: linux-pm@...r.kernel.org
>> Cc: linuxppc-dev@...ts.ozlabs.org
>> Cc: Srivatsa S. Bhat <srivatsa@....edu>
>> Cc: Preeti U. Murthy <preeti@...ux.vnet.ibm.com>
>> Cc: Vaidyanathan Srinivasan <svaidy@...ux.vnet.ibm.com>
>>
>> v2:
>> Rebased on 3.17-rc7
>> Split from 'powerpc/powernv: Support for fastsleep and winkle'
>>
>> v1:
>> https://lkml.org/lkml/2014/8/25/446
>>
>> Preeti U Murthy (1):
>>   powerpc/powernv/cpuidle: Add workaround to enable fastsleep
>>
>> Shreyas B. Prabhu (1):
>>   powerpc/kvm/book3s_hv: Enable CPUs to run guest after waking up from
>>     fast-sleep
>>
>> Srivatsa S. Bhat (1):
>>   powerpc/powernv: Enable Offline CPUs to enter deep idle states
>>
>>  arch/powerpc/include/asm/machdep.h             |   3 +
>>  arch/powerpc/include/asm/opal.h                |   7 ++
>>  arch/powerpc/include/asm/processor.h           |   4 +-
>>  arch/powerpc/kernel/exceptions-64s.S           |  35 ++++----
>>  arch/powerpc/kernel/idle.c                     |  19 ++++
>>  arch/powerpc/kernel/idle_power7.S              |   2 +-
>>  arch/powerpc/platforms/powernv/opal-wrappers.S |   1 +
>>  arch/powerpc/platforms/powernv/powernv.h       |   7 ++
>>  arch/powerpc/platforms/powernv/setup.c         | 118 +++++++++++++++++++++++++
>>  arch/powerpc/platforms/powernv/smp.c           |  11 ++-
>>  drivers/cpuidle/cpuidle-powernv.c              |  13 ++-
>>  11 files changed, 194 insertions(+), 26 deletions(-)
> 
> [2/3] seems to be missig from the series.
> 
> Also, since that mostly modifies arch/powerpc, I think it should go through
> that tree.  I'm fine with the cpuidle-powernv changes in [1/3] and [3/3].
> 
Hi Rafael, 

Thanks for looking into this. The second patch is an independent fix in the 
powerpc exception handler. To be safe I am ccing you and linux-pm list on that
patch now. 


Thanks, 
Shreyas

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