Re: [PATCH 04/13] x86, mm: Revert back good_end setting for 64bit

[H. Peter Anvin]

On 10/05/2012 02:32 PM, Eric W. Biederman wrote:
> Yinghai Lu <yinghai@xxxxxxxxxx> writes:
>
> > On Fri, Oct 5, 2012 at 2:04 PM, Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote:
> > > > > Is there a git commit that explains what the 'big range' problem is?
> > >
> > > At least on x86_64 this was recently tested and anywhere below 4G is
> > > good, and there is a patch floating around somewhere to remove this
> > > issue.
> >
> > patch for kernel or kexec-tools?
>
> kernel.
>
> The sgi guys needed a kdump kernel with 1G of ram to dump their all of
> the memory on one of their crazy large machines and so investigated
> this.
>
> Basically they found that a kdump kernel loaded anywhere < 4G worked,
> the only change that was needed was to relaxy the 896M hard code.
>
> In one test they had a kdump kernel loaded above 2G.

Seriously, any case where we can't load anywhere in physical ram on 
x86-64 is a bug.  i386 is another matter.

	-hpa

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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