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Re: [Xen-devel] [RFC PATCH v1 01/33] mm: introduce common help functions to deal with reserved/managed pages
- To: Sam Ravnborg <sam@xxxxxxxxxxxx>
- From: Russell King - ARM Linux <linux@xxxxxxxxxxxxxxxx>
- Date: Wed, 6 Mar 2013 17:21:41 +0000
- Cc: xen-devel@xxxxxxxxxxxxxxxxxxx, Jeremy Fitzhardinge <jeremy@xxxxxxxx>, x86@xxxxxxxxxx, Aurelien Jacquiot <a-jacquiot@xxxxxx>, Catalin Marinas <catalin.marinas@xxxxxxx>, Heiko Carstens <heiko.carstens@xxxxxxxxxx>, Tang Chen <tangchen@xxxxxxxxxxxxxx>, David Howells <dhowells@xxxxxxxxxx>, Chen Liqin <liqin.chen@xxxxxxxxxxxxx>, Paul Mackerras <paulus@xxxxxxxxx>, "H. Peter Anvin" <hpa@xxxxxxxxx>, Guan Xuetao <gxt@xxxxxxxxxxxxxxx>, Lennox Wu <lennox.wu@xxxxxxxxx>, Maciej Rutecki <maciej.rutecki@xxxxxxxxx>, Jonas Bonn <jonas@xxxxxxxxxxxx>, Mark Salter <msalter@xxxxxxxxxx>, Michel Lespinasse <walken@xxxxxxxxxx>, Mikael Starvik <starvik@xxxxxxxx>, Yoshinori Sato <ysato@xxxxxxxxxxxxxxxxxxxx>, Helge Deller <deller@xxxxxx>, Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>, "James E.J. Bottomley" <jejb@xxxxxxxxxxxxxxxx>, Yasuaki Ishimatsu <isimatu.yasuaki@xxxxxxxxxxxxxx>, Ingo Molnar <mingo@xxxxxxxxxx>, Geert Uytterhoeven <geert@xxxxxxxxxxxxxx>, Mel Gorman <mgorman@xxxxxxx>, Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>, Matt Turner <mattst88@xxxxxxxxx>, Anatolij Gustschin <agust@xxxxxxx>, linux-mm@xxxxxxxxx, Jiang Liu <liuj97@xxxxxxxxx>, Fenghua Yu <fenghua.yu@xxxxxxxxx>, Rusty Russell <rusty@xxxxxxxxxxxxxxx>, Mike Frysinger <vapier@xxxxxxxxxx>, Jiang Liu <jiang.liu@xxxxxxxxxx>, Wen Congyang <wency@xxxxxxxxxxxxxx>, Chris Zankel <chris@xxxxxxxxxx>, Will Deacon <will.deacon@xxxxxxx>, Jeff Dike <jdike@xxxxxxxxxxx>, Chris Clayton <chris2553@xxxxxxxxxxxxxx>, Hans-Christian Egtvedt <egtvedt@xxxxxxxxxxxx>, Chris Metcalf <cmetcalf@xxxxxxxxxx>, "Rafael J . Wysocki" <rjw@xxxxxxx>, Tony Luck <tony.luck@xxxxxxxxx>, Ivan Kokshaysky <ink@xxxxxxxxxxxxxxxxxxxx>, Jianguo Wu <wujianguo@xxxxxxxxxx>, Thomas Gleixner <tglx@xxxxxxxxxxxxx>, virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx, Yinghai Lu <yinghai@xxxxxxxxxx>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>, Richard Henderson <rth@xxxxxxxxxxx>, linux-arm-kernel@xxxxxxxxxxxxxxxxxxx, Michal Hocko <mhocko@xxxxxxx>, Michal Simek <monstr@xxxxxxxxx>, Koichi Yasutake <yasutake.koichi@xxxxxxxxxxxxxxxx>, Max Filippov <jcmvbkbc@xxxxxxxxx>, Hirokazu Takata <takata@xxxxxxxxxxxxxx>, linux-kernel@xxxxxxxxxxxxxxx, Ralf Baechle <ralf@xxxxxxxxxxxxxx>, Minchan Kim <minchan@xxxxxxxxxx>, Paul Mundt <lethal@xxxxxxxxxxxx>, "Michael S. Tsirkin" <mst@xxxxxxxxxx>, Eric Biederman <ebiederm@xxxxxxxxxxxx>, Martin Schwidefsky <schwidefsky@xxxxxxxxxx>, David Rientjes <rientjes@xxxxxxxxxx>, Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>, Haavard Skinnemoen <hskinnemoen@xxxxxxxxx>, "David S. Miller" <davem@xxxxxxxxxxxxx>
- Delivery-date: Wed, 06 Mar 2013 17:35:16 +0000
- List-id: Xen developer discussion <xen-devel.lists.xen.org>
On Tue, Mar 05, 2013 at 08:47:22PM +0100, Sam Ravnborg wrote:
> On Tue, Mar 05, 2013 at 10:54:44PM +0800, Jiang Liu wrote:
> > +static inline void free_initmem_default(int poison)
> > +{
>
> Why request user to supply the poison argumet. If this is the default
> implmentation then use the default poison value too (POISON_FREE_INITMEM)
That poison value is inappropriate on some architectures like ARM - it's
executable. The default poison value leads to:
0: cccccccc stclgt 12, cr12, [ip], {204} ; 0xcc
or
4: cccc ldmia r4!, {r2, r3, r6, r7}
And we might as well forget using any kind of poison in that case.
The value which use is an undefined instruction on ARM and Thumb.
Notice the calls to poison_init_mem() in arch/arm/mm/init.c, which are
left by these patches, allowing us to continue using an appropriate
architecture specific value which will help to ensure that people
calling discarded init functions get appropriately bitten.
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