linux-kernel - Re: [PATCH] x86 e820: only void usable memory areas in memmap=exactmap case

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Date:	Fri, 11 Jan 2013 19:24:41 +0100
From:	Thomas Renninger <trenn@...e.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	MUNEDA Takahiro <muneda.takahiro@...fujitsu.com>,
	Takao Indoh <indou.takao@...fujitsu.com>,
	linux-pci@...r.kernel.org, x86@...nel.org,
	linux-kernel@...r.kernel.org, andi@...stfloor.org,
	tokunaga.keiich@...fujitsu.com, kexec@...ts.infradead.org,
	hbabu@...ibm.com, mingo@...hat.com, ddutile@...hat.com,
	vgoyal@...hat.com, ishii.hironobu@...fujitsu.com, hpa@...or.com,
	bhelgaas@...gle.com, tglx@...utronix.de, khalid@...ehiking.org,
	horms@...ge.net.au
Subject: Re: [PATCH] x86 e820: only void usable memory areas in memmap=exactmap case

On Friday, January 11, 2013 08:16:52 AM Yinghai Lu wrote:
> On Fri, Jan 11, 2013 at 4:33 AM, Thomas Renninger <trenn@...e.de> wrote:
...
> > -               e820.nr_map = 0;
> > +               /*
> > +                * Remove all usable memory (this is for kdump), usable
> > +                * memory will be passed via memmap=X@Y parameter
> > +                */
> > +               e820_remove_range_type(E820_RAM);
> 
> We may need to keep exactmap intact.
Why?
Kexec/kdump should have been the only user?
If older/current kexec calls still add ACPI maps via memmap=X#Y,
they should already exist in the original e820 map and fall off or
get glued to one region if (wrongly) overlapping via sanitize_map.
 
> but could add another one like exact_ram_map
> or extend to have memmap=exactmap=ram or etc.

I would avoid that if anyhow possible because then you run into
kexec vs kernel version problems.

Maybe I should explicitly post (out of this thread) the patch to the
kexec list.
If nobody can come up with a strong reason, it should be ok?

   Thomas
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