No subject

[Dave Young]

vgoyal at redhat.com
	linux-kernel at vger.kernel.org,
	Eric Biederman <ebiederm at xmission.com>
Bcc: ruyang at redhat.com
Subject: Re: [PATCH v3 3/9] kexec_file: Factor out kexec_locate_mem_hole from
 kexec_add_buffer.
Reply-To: 
In-Reply-To: <5428891.iJNV8CI1We at hactar>

On 06/27/16 at 01:37pm, Thiago Jung Bauermann wrote:
> Am Dienstag, 28 Juni 2016, 00:19:48 schrieb Dave Young:
> > On 06/23/16 at 12:37pm, Thiago Jung Bauermann wrote:
> > > Am Donnerstag, 23 Juni 2016, 01:44:07 schrieb Dave Young:
> > > What is bad about the description of top_down?
> > It is not clear enough to me, I personally think the original one in
> > source code is better:
> > /* allocate from top of memory hole */
> 
> Actually I realized there's some discrepancy in how the x86 code uses 
> top_down and how I need it to work in powerpc. This may be what is confusing 
> about my comment and the existing comment.
> 
> x86 always walks memory from bottom to top but if top_down is true, in each 
> memory region it will allocate the memory hole in the highest address within 
> that region. I don't know why it is done that way, though.

I think we did not meaning to do this, considering kdump we have only
one crashkernel region for searching (crashk_res) so it is fine.
For kexec maybe changing the walking function to accept top_down is
reasonable.

Ccing Vivek see if he can remember something..

> 
> On powerpc, the memory walk itself should be from top to bottom, as well as 
> the memory hole allocation within each memory region.
> 
> Should I add a separate top_down argument to kexec_locate_mem_hole to 
> control if the memory walk should be from top to bottom, and then the 
> bottom_up member of struct kexec_buf controls where inside each memory 
> region the memory hole will be allocated?
> 
> -- 
> []'s
> Thiago Jung Bauermann
> IBM Linux Technology Center
> 
> 
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Thanks
Dave