linux-kernel - Re: [PATCH v3 5/6] arch: introduce memremap_cache() and memremap

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Date:	Mon, 8 Jun 2015 11:25:28 -0700
From:	Dan Williams <dan.j.williams@...el.com>
To:	Andy Shevchenko <andy.shevchenko@...il.com>
Cc:	Arnd Bergmann <arnd@...db.de>, Ingo Molnar <mingo@...hat.com>,
	Borislav Petkov <bp@...en8.de>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ross Zwisler <ross.zwisler@...ux.intel.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Juergen Gross <jgross@...e.com>,
	"x86@...nel.org" <x86@...nel.org>,
	"Kani, Toshimitsu" <toshi.kani@...com>,
	"linux-nvdimm@...ts.01.org" <linux-nvdimm@...ts.01.org>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Luis Rodriguez <mcgrof@...e.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Stefan Bader <stefan.bader@...onical.com>,
	Andy Lutomirski <luto@...capital.net>, linux-mm@...ck.org,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Ralf Baechle <ralf@...ux-mips.org>,
	Henrique de Moraes Holschuh <hmh@....eng.br>,
	mpe@...erman.id.au, Tejun Heo <tj@...nel.org>,
	Paul Mackerras <paulus@...ba.org>,
	Christoph Hellwig <hch@....de>
Subject: Re: [PATCH v3 5/6] arch: introduce memremap_cache() and memremap_wt()

On Mon, Jun 8, 2015 at 9:27 AM, Andy Shevchenko
<andy.shevchenko@...il.com> wrote:
> On Thu, Jun 4, 2015 at 12:34 AM, Dan Williams <dan.j.williams@...el.com> wrote:
>> Existing users of ioremap_cache() are mapping memory that is known in
>> advance to not have i/o side effects.  These users are forced to cast
>> away the __iomem annotation, or otherwise neglect to fix the sparse
>> errors thrown when dereferencing pointers to this memory.  Provide
>> memremap_*() as a non __iomem annotated ioremap_*().
>>
>> The ARCH_HAS_MEMREMAP kconfig symbol is introduced for archs to assert
>> that it is safe to recast / reuse the return value from ioremap as a
>> normal pointer to memory.  In other words, archs that mandate specific
>> accessors for __iomem are not memremap() capable and drivers that care,
>> like pmem, can add a dependency to disable themselves on these archs.
>
> One minor comment. Otherwise looks good for me.
>
> []
>
>> --- a/kernel/resource.c
>> +++ b/kernel/resource.c
>
>> @@ -528,6 +528,45 @@ int region_is_ram(resource_size_t start, unsigned long size)
>>         return ret;
>>  }
>>
>> +#ifdef CONFIG_ARCH_HAS_MEMREMAP
>> +/*
>> + * memremap() is "ioremap" for cases where it is known that the resource
>> + * being mapped does not have i/o side effects and the __iomem
>> + * annotation is not applicable.
>> + */
>> +static bool memremap_valid(resource_size_t offset, size_t size)
>> +{
>> +       if (region_is_ram(offset, size) != 0) {
>> +               WARN_ONCE(1, "memremap attempted on ram %pa size: %zd\n",
>
> %zu

Sure, thanks for taking a look Andy!
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