linux-kernel - Re: [PATCH 01/11] resource: Add System RAM resource type

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Date:	Wed, 16 Dec 2015 13:26:42 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Toshi Kani <toshi.kani@....com>
Cc:	akpm@...ux-foundation.org, linux-arch@...r.kernel.org,
	linux-mm@...ck.org, linux-kernel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Dan Williams <dan.j.williams@...el.com>
Subject: Re: [PATCH 01/11] resource: Add System RAM resource type

On Mon, Dec 14, 2015 at 04:37:16PM -0700, Toshi Kani wrote:
> I/O resource type, IORESOURCE_MEM, is used for all types of
> memory-mapped ranges, ex. System RAM, System ROM, Video RAM,
> Persistent Memory, PCI Bus, PCI MMCONFIG, ACPI Tables, IOAPIC,
> reserved, and so on.  This requires walk_system_ram_range(),
> walk_system_ram_res(), and region_intersects() to use strcmp()
> against string "System RAM" to search System RAM ranges in the
> iomem table, which is inefficient.  __ioremap_caller() and
> reserve_memtype() on x86, for instance, call walk_system_ram_range()
> for every request to check if a given range is in System RAM ranges.
> 
> However, adding a new I/O resource type for System RAM is not
> a viable option [1].

I think you should explain here why it isn't a viable option instead of
quoting some flaky reference which might or might not be there in the
future.

> Instead, this patch adds a new modifier
> flag IORESOURCE_SYSRAM to IORESOURCE_MEM, which introduces an
> extended I/O resource type, IORESOURCE_SYSTEM_RAM [2].
> 
> To keep the code 'if (resource_type(r) == IORESOURCE_MEM)' to
> work continuously for System RAM, resource_ext_type() is added
> for extracting extended type bit(s).
> 
> Cc: Linus Torvalds <torvalds@...ux-foundation.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Borislav Petkov <bp@...en8.de>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> Cc: Dan Williams <dan.j.williams@...el.com>
> Reference[1]: https://lkml.org/lkml/2015/12/3/540
> Reference[2]: https://lkml.org/lkml/2015/12/3/582

References should look something like this:

Link: http://lkml.kernel.org/r/<Message-ID>

> Signed-off-by: Toshi Kani <toshi.kani@....com>
> ---
>  include/linux/ioport.h |   11 +++++++++++
>  1 file changed, 11 insertions(+)
> 
> diff --git a/include/linux/ioport.h b/include/linux/ioport.h
> index 24bea08..4b65d94 100644
> --- a/include/linux/ioport.h
> +++ b/include/linux/ioport.h
> @@ -49,12 +49,19 @@ struct resource {
>  #define IORESOURCE_WINDOW	0x00200000	/* forwarded by bridge */
>  #define IORESOURCE_MUXED	0x00400000	/* Resource is software muxed */
>  
> +#define IORESOURCE_EXT_TYPE_BITS 0x01000000	/* Resource extended types */

Should this be 0x07000000 so that we make all there bits belong to the
extended types? Are we going to need so many?

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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