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Subject: Re: [PATCH v12 04/31] arm64/mm: define
 ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT
To:     Mark Rutland <mark.rutland@arm.com>
Cc:     Jerome Glisse <jglisse@redhat.com>, akpm@linux-foundation.org,
        mhocko@kernel.org, peterz@infradead.org, kirill@shutemov.name,
        ak@linux.intel.com, dave@stgolabs.net, jack@suse.cz,
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        aneesh.kumar@linux.ibm.com, benh@kernel.crashing.org,
        mpe@ellerman.id.au, paulus@samba.org,
        Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, hpa@zytor.com,
        Will Deacon <will.deacon@arm.com>,
        Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
        sergey.senozhatsky.work@gmail.com,
        Andrea Arcangeli <aarcange@redhat.com>,
        Alexei Starovoitov <alexei.starovoitov@gmail.com>,
        kemi.wang@intel.com, Daniel Jordan <daniel.m.jordan@oracle.com>,
        David Rientjes <rientjes@google.com>,
        Ganesh Mahendran <opensource.ganesh@gmail.com>,
        Minchan Kim <minchan@kernel.org>,
        Punit Agrawal <punitagrawal@gmail.com>,
        vinayak menon <vinayakm.list@gmail.com>,
        Yang Shi <yang.shi@linux.alibaba.com>,
        zhong jiang <zhongjiang@huawei.com>,
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        Mike Rapoport <rppt@linux.ibm.com>,
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        haren@linux.vnet.ibm.com, npiggin@gmail.com,
        paulmck@linux.vnet.ibm.com, Tim Chen <tim.c.chen@linux.intel.com>,
        linuxppc-dev@lists.ozlabs.org, x86@kernel.org
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 <20190418215113.GD11645@redhat.com>
 <73a3650d-7e9f-bc9e-6ea1-2cef36411b0c@linux.ibm.com>
 <20190423161931.GE56999@lakrids.cambridge.arm.com>
From:   Laurent Dufour <ldufour@linux.ibm.com>
Date:   Wed, 24 Apr 2019 12:34:34 +0200
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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@gmail.com>
>>>>>>>
>>>>>>> Set ARCH_SUPPORTS_SPECULATIVE_PAGE_FAULT for arm64. This
>>>>>>> enables Speculative Page Fault handler.
>>>>>>>
>>>>>>> Signed-off-by: Ganesh Mahendran <opensource.ganesh@gmail.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@redhat.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.