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Message-ID: <20160627202125.GA9230@dhcp-128-65.nay.redhat.com>
Date: Mon, 27 Jun 2016 16:21:25 -0400
From: Dave Young <dyoung@...hat.com>
To: Thiago Jung Bauermann <bauerman@...ux.vnet.ibm.com>
Cc: kexec@...ts.infradead.org, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, vgoyal@...hat.com,
Eric Biederman <ebiederm@...ssion.com>
Subject: Re: [PATCH v3 3/9] kexec_file: Factor out kexec_locate_mem_hole from
kexec_add_buffer.
Please ignore previous reply, I mistakenly send a broken mail without
subject, sorry about it. Resend the reply here.
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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