linux-kernel - Re: [PATCH v12 0/10] Support Write-Through mapping on x86

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Date:	Tue, 2 Jun 2015 12:50:09 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	"Luis R. Rodriguez" <mcgrof@...e.com>
Cc:	Toshi Kani <toshi.kani@...com>, Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	X86 ML <x86@...nel.org>,
	linux-nvdimm <linux-nvdimm@...ts.01.org>,
	Juergen Gross <jgross@...e.com>,
	Stefan Bader <stefan.bader@...onical.com>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	Yigal Korman <yigal@...xistor.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"Elliott, Robert (Server Storage)" <Elliott@...com>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v12 0/10] Support Write-Through mapping on x86

On Tue, Jun 2, 2015 at 12:43 PM, Luis R. Rodriguez <mcgrof@...e.com> wrote:
> On Tue, Jun 02, 2015 at 12:46:48PM -0600, Toshi Kani wrote:
>> On Tue, 2015-06-02 at 18:21 +0200, Luis R. Rodriguez wrote:
>> > On Mon, Jun 01, 2015 at 01:36:23PM -0600, Toshi Kani wrote:
>> > > This patchset adds support of Write-Through (WT) mapping on x86.
>> > > The study below shows that using WT mapping may be useful for
>> > > non-volatile memory.
>> > >
>> > > http://www.hpl.hp.com/techreports/2012/HPL-2012-236.pdf
>> > >
>> > > The patchset consists of the following changes.
>> > >  - Patch 1/10 to 6/10 add ioremap_wt()
>> > >  - Patch 7/10 adds pgprot_writethrough()
>> > >  - Patch 8/10 to 9/10 add set_memory_wt()
>> > >  - Patch 10/10 changes the pmem driver to call ioremap_wt()
>> > >
>> > > All new/modified interfaces have been tested.
>> > >
>> > > The patchset is based on:
>> > > git://git.kernel.org/pub/scm/linux/kernel/git/bp/bp.git#tip-mm-2
>> >
>> > While at it can you also look at:
>> >
>> > mcgrof@...on ~/linux-next (git::master)$ git grep -4 "writethrough" drivers/infiniband/
>>
>> Thanks for checking this.  The inifiniband driver uses WT mappings on
>> powerpc without proper WT interfaces defined.
>
> Right.
>
>>  They can be cleaned up by
>> a separate patch series to support WT on powerpc in the same way after
>> this patchset (support WT on x86) is settled.
>
> Who's gonna do that work though? How much work is it ? Is it too much to ask
> to roll it in this series?
>

I think the driver maintainers should do it.  For all I know,
something will go horribly wrong if those drivers suddenly start using
WT on x86.

--Andy
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