From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>,
Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org
Subject: Re: [patch] bootmem: use MAX_DMA_ADDRESS instead of LOW32LIMIT
Date: Fri, 28 Jul 2006 16:58:45 +0200 [thread overview]
Message-ID: <1154098725.3211.5.camel@localhost> (raw)
In-Reply-To: <20060728131306.GA32513@elte.hu>
On Fri, 2006-07-28 at 15:13 +0200, Ingo Molnar wrote:
> > -#define LOW32LIMIT 0xffffffff
>
> > if ((ptr = __alloc_bootmem_core(bdata, size,
> > - align, goal, LOW32LIMIT)))
> > + align, goal, MAX_DMA_ADDRESS)))
>
> but this limits things to 16MB on i686. Are you sure this wont break
> anything?
That is something we should not do. MAX_DMA_ADDRESS is not the correct
value, it says something about the DMA limitations. LOW32LIMIT says
something about the cpu addressing limitations which is a completly
different thing. I think it would be best to introduce an architecture
overridable define like LOW_ADDRESS_LIMIT. The default is 4GB-1, for
s390 it is 2GB-1. The current name is misleading LOW32LIMIT indicates
that the address for alloc_bootmem_low objects has 32 bits, which isn't
true for s390.
--
blue skies,
Martin.
Martin Schwidefsky
Linux for zSeries Development & Services
IBM Deutschland Entwicklung GmbH
"Reality continues to ruin my life." - Calvin.
next prev parent reply other threads:[~2006-07-28 14:58 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-07-28 13:08 [patch] bootmem: use MAX_DMA_ADDRESS instead of LOW32LIMIT Heiko Carstens
2006-07-28 13:13 ` Ingo Molnar
2006-07-28 14:58 ` Martin Schwidefsky [this message]
2006-07-28 19:41 ` Heiko Carstens
2006-07-29 3:55 ` Ingo Molnar
2006-08-07 5:27 ` Randy.Dunlap
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