linux-kernel - Re: [PATCH v12 04/31] arm64/mm: define ARCH_SUPPORTS_SPECULATIVE_PAGE

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Date:   Wed, 24 Apr 2019 12:34:34 +0200
From:   Laurent Dufour <ldufour@...ux.ibm.com>
To:     Mark Rutland <mark.rutland@....com>
Cc:     Jerome Glisse <jglisse@...hat.com>, akpm@...ux-foundation.org,
        mhocko@...nel.org, peterz@...radead.org, kirill@...temov.name,
        ak@...ux.intel.com, dave@...olabs.net, jack@...e.cz,
        Matthew Wilcox <willy@...radead.org>,
        aneesh.kumar@...ux.ibm.com, benh@...nel.crashing.org,
        mpe@...erman.id.au, paulus@...ba.org,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
        Will Deacon <will.deacon@....com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        sergey.senozhatsky.work@...il.com,
        Andrea Arcangeli <aarcange@...hat.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        kemi.wang@...el.com, Daniel Jordan <daniel.m.jordan@...cle.com>,
        David Rientjes <rientjes@...gle.com>,
        Ganesh Mahendran <opensource.ganesh@...il.com>,
        Minchan Kim <minchan@...nel.org>,
        Punit Agrawal <punitagrawal@...il.com>,
        vinayak menon <vinayakm.list@...il.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>,
        zhong jiang <zhongjiang@...wei.com>,
        Haiyan Song <haiyanx.song@...el.com>,
        Balbir Singh <bsingharora@...il.com>, sj38.park@...il.com,
        Michel Lespinasse <walken@...gle.com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, npiggin@...il.com,
        paulmck@...ux.vnet.ibm.com, Tim Chen <tim.c.chen@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH v12 04/31] arm64/mm: define
 ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT

Le 23/04/2019 à 18:19, Mark Rutland a écrit :
> On Tue, Apr 23, 2019 at 05:36:31PM +0200, Laurent Dufour wrote:
>> Le 18/04/2019 à 23:51, Jerome Glisse a écrit :
>>> On Tue, Apr 16, 2019 at 03:41:56PM +0100, Mark Rutland wrote:
>>>> On Tue, Apr 16, 2019 at 04:31:27PM +0200, Laurent Dufour wrote:
>>>>> Le 16/04/2019 à 16:27, Mark Rutland a écrit :
>>>>>> On Tue, Apr 16, 2019 at 03:44:55PM +0200, Laurent Dufour wrote:
>>>>>>> From: Mahendran Ganesh <opensource.ganesh@...il.com>
>>>>>>>
>>>>>>> Set ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT for arm64. This
>>>>>>> enables Speculative Page Fault handler.
>>>>>>>
>>>>>>> Signed-off-by: Ganesh Mahendran <opensource.ganesh@...il.com>
>>>>>>
>>>>>> This is missing your S-o-B.
>>>>>
>>>>> You're right, I missed that...
>>>>>
>>>>>> The first patch noted that the ARCH_SUPPORTS_* option was there because
>>>>>> the arch code had to make an explicit call to try to handle the fault
>>>>>> speculatively, but that isn't addeed until patch 30.
>>>>>>
>>>>>> Why is this separate from that code?
>>>>>
>>>>> Andrew was recommended this a long time ago for bisection purpose. This
>>>>> allows to build the code with CONFIG_SPECULATIVE_PAGE_FAULT before the code
>>>>> that trigger the spf handler is added to the per architecture's code.
>>>>
>>>> Ok. I think it would be worth noting that in the commit message, to
>>>> avoid anyone else asking the same question. :)
>>>
>>> Should have read this thread before looking at x86 and ppc :)
>>>
>>> In any case the patch is:
>>>
>>> Reviewed-by: Jérôme Glisse <jglisse@...hat.com>
>>
>> Thanks Mark and Jérôme for reviewing this.
>>
>> Regarding the change in the commit message, I'm wondering if this would be
>> better to place it in the Series's letter head.
>>
>> But I'm fine to put it in each architecture's commit.
> 
> I think noting it in both the cover letter and specific patches is best.
> 
> Having something in the commit message means that the intent will be
> clear when the patch is viewed in isolation (e.g. as they will be once
> merged).
> 
> All that's necessary is something like:
> 
>    Note that this patch only enables building the common speculative page
>    fault code such that this can be bisected, and has no functional
>    impact. The architecture-specific code to make use of this and enable
>    the feature will be addded in a subsequent patch.

Thanks Mark, will do it this way.


> Thanks,
> Mark.