linux-kernel - Re: [PATCH resend 0/3] mm: allow arch to override lowmem_page

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Message-ID: <20160422090744.GB4236@arm.com>
Date:	Fri, 22 Apr 2016 10:07:45 +0100
From:	Will Deacon <will.deacon@....com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org, lftan@...era.com,
	jonas@...thpole.se
Subject: Re: [PATCH resend 0/3] mm: allow arch to override lowmem_page_address

On Thu, Apr 21, 2016 at 04:51:38PM -0700, Andrew Morton wrote:
> On Mon, 18 Apr 2016 18:04:54 +0200 Ard Biesheuvel <ard.biesheuvel@...aro.org> wrote:
> 
> > These patches allow the arch to define the page_to_virt() conversion that
> > is used in lowmem_page_address(). This is desirable for arm64, where this
> > conversion is trivial when CONFIG_SPARSEMEM_VMEMMAP is enabled, while
> > breaking it up into __va(PFN_PHYS(page_to_pfn(page))), as is done currently
> > in lowmem_page_address(), will force the use of a virt-to-phys() conversion
> > and back again, which always involves a memory access on arm64, since the
> > start of physical memory is not a compile time constant.
> > 
> > I have split off these patches from my series 'arm64: optimize virt_to_page
> > and page_address' which I sent out 3 weeks ago, and resending them in the
> > hope that they can be picked up (with Will's ack on #3) to be merged via
> > the mm tree.
> > 
> > I have cc'ed the nios2 and openrisc maintainers on previous versions, and
> > cc'ing them again now. I have dropped both of the arch specific mailing
> > lists, since one is defunct and the other is subscriber only.
> > 
> > Andrew, is this something you would be pulling to pick up (assuming that you
> > agree with the contents)? Thanks.
> 
> Looks OK to me and apart from the trivial openrisc/nios2 changes it's
> obviously a no-op for all-but-arm.  So I suggest you include these
> patches in the appropriate arm tree.
> 
> Acked-by: Andrew Morton <akpm@...ux-foundation.org>

Cracking, thanks Andrew. I'll queue these three in the arm64 tree and get
them into -next.

Will