linux-kernel - Re: [PATCH v9 01/24] mm: Introduce CONFIG_SPECULATIVE_PAGE

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Date:   Wed, 28 Mar 2018 09:49:29 +0200
From:   Laurent Dufour <ldufour@...ux.vnet.ibm.com>
To:     David Rientjes <rientjes@...gle.com>,
        Thomas Gleixner <tglx@...utronix.de>
Cc:     paulmck@...ux.vnet.ibm.com, peterz@...radead.org,
        akpm@...ux-foundation.org, kirill@...temov.name,
        ak@...ux.intel.com, mhocko@...nel.org, dave@...olabs.net,
        jack@...e.cz, Matthew Wilcox <willy@...radead.org>,
        benh@...nel.crashing.org, mpe@...erman.id.au, paulus@...ba.org,
        Ingo Molnar <mingo@...hat.com>, hpa@...or.com,
        Will Deacon <will.deacon@....com>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>,
        kemi.wang@...el.com, sergey.senozhatsky.work@...il.com,
        Daniel Jordan <daniel.m.jordan@...cle.com>,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        haren@...ux.vnet.ibm.com, khandual@...ux.vnet.ibm.com,
        npiggin@...il.com, bsingharora@...il.com,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        linuxppc-dev@...ts.ozlabs.org, x86@...nel.org
Subject: Re: [PATCH v9 01/24] mm: Introduce CONFIG_SPECULATIVE_PAGE_FAULT

Hi David,

Thanks a lot for your deep review on this series.

On 25/03/2018 23:50, David Rientjes wrote:
> On Tue, 13 Mar 2018, Laurent Dufour wrote:
> 
>> This configuration variable will be used to build the code needed to
>> handle speculative page fault.
>>
>> By default it is turned off, and activated depending on architecture
>> support.
>>
>> Suggested-by: Thomas Gleixner <tglx@...utronix.de>
>> Signed-off-by: Laurent Dufour <ldufour@...ux.vnet.ibm.com>
>> ---
>>  mm/Kconfig | 3 +++
>>  1 file changed, 3 insertions(+)
>>
>> diff --git a/mm/Kconfig b/mm/Kconfig
>> index abefa573bcd8..07c566c88faf 100644
>> --- a/mm/Kconfig
>> +++ b/mm/Kconfig
>> @@ -759,3 +759,6 @@ config GUP_BENCHMARK
>>  	  performance of get_user_pages_fast().
>>  
>>  	  See tools/testing/selftests/vm/gup_benchmark.c
>> +
>> +config SPECULATIVE_PAGE_FAULT
>> +       bool
> 
> Should this be configurable even if the arch supports it?

Actually, this is not configurable unless by manually editing the .config file.

I made it this way on the Thomas's request :
https://lkml.org/lkml/2018/1/15/969

That sounds to be the smarter way to achieve that, isn't it ?

Laurent.