linux-kernel - Re: [PATCH v7 24/27] x86: Add swiotlb force off support

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Date:	Mon, 24 Dec 2012 15:34:09 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Yinghai Lu <yinghai@...nel.org>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 24/27] x86: Add swiotlb force off support

On 12/21/2012 09:11 PM, Yinghai Lu wrote:
> On Fri, Dec 21, 2012 at 7:25 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> On 12/21/2012 07:23 PM, Eric W. Biederman wrote:
>>>
>>> In this case YH has been working on the case of loading a kernel
>>> completely above 4G, and apparently he has also been testing the case of
>>> running a kernel with no memory below 4G.
>>>
>>
>> It is worth noting that we cannot run with *no* memory below 4G -- it is
>> not possible to run SMP at least without some memory below the 1M mark.
> 
> yes need keep 8k or so for trampoline.
> 
> but kdump only use one CPU.
> 

... except we have an active request to change that, and the trampoline
is more like 20K depending on options.

	-hpa


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