linux-kernel - Re: [RFC PATCH 1/2] memremap: add arch specific hook for MEMREMAP

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Message-ID: <CAPcyv4ivN9c8PHBR77vd36ovB28OETJUr6VYf_8gNtXgqEmATw@mail.gmail.com>
Date:	Mon, 22 Feb 2016 11:05:51 -0800
From:	Dan Williams <dan.j.williams@...el.com>
To:	Ard Biesheuvel <ard.biesheuvel@...aro.org>
Cc:	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Russell King - ARM Linux <linux@....linux.org.uk>,
	Arnd Bergmann <arnd@...db.de>, nico@...aro.org
Subject: Re: [RFC PATCH 1/2] memremap: add arch specific hook for MEMREMAP_WB mappings

On Mon, Feb 22, 2016 at 6:02 AM, Ard Biesheuvel
<ard.biesheuvel@...aro.org> wrote:
> Currently, the memremap code serves MEMREMAP_WB mappings directly from
> the kernel direct mapping, unless the region is in high memory, in which
> case it falls back to using ioremap_cache(). However, the semantics of
> ioremap_cache() are not unambiguously defined, and on ARM, it will
> actually result in a mapping type that differs from the attributes used
> for the linear mapping, and for this reason, the ioremap_cache() call
> fails if the region is part of the memory managed by the kernel.
>
> So instead, implement an optional hook 'arch_memremap_wb' whose default
> implementation calls ioremap_cache() as before, but which can be
> overridden by the architecture to do what is appropriate for it.
>

Acked-by: Dan Williams <dan.j.williams@...el.com>

I still have patches pending to delete ioremap_cache() from ARM and
require memremap() to be used for cacheable mappings.  Do you see any
use for ioremap_cache() on ARM after this change?