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

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Message-ID: <20190416144156.GB54708@lakrids.cambridge.arm.com>
Date:   Tue, 16 Apr 2019 15:41:56 +0100
From:   Mark Rutland <mark.rutland@....com>
To:     Laurent Dufour <ldufour@...ux.ibm.com>
Cc:     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>,
        Jerome Glisse <jglisse@...hat.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

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. :)

Thanks,
Mark.