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

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Message-ID: <1824463.EWDqkMLC4N@hammer82.arch.suse.de>
Date:	Tue, 15 Jan 2013 01:54:55 +0100
From:	Thomas Renninger <trenn@...e.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	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,
	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 Monday, January 14, 2013 11:04:36 AM Yinghai Lu wrote:
> On Mon, Jan 14, 2013 at 7:05 AM, Thomas Renninger <trenn@...e.de> wrote:
> > What is this for?:
> > @@ -871,6 +879,11 @@ static int __init parse_memmap_one(char
> > 
> >         userdef = 1;
> >         if (*p == '@') {
> >         
> >                 start_at = memparse(p+1, &p);
> > 
> > +               if (exactusablemap_parsed) {
> > +                       /* remove all range with other types */
> > +                       e820_remove_range(start_at, mem_size,
> > +                                                E820_RAM, 0);
> > +               }
> > 
> >                 e820_add_region(start_at, mem_size, E820_RAM);
> >         
> >         } else if (*p == '#') {
> >         
> >                 start_at = memparse(p+1, &p);
> 
> remove all old renges before add E820_RAM, otherwise new add E820
> ranges could be ignored.
But this is intended?
kexec must never request reserved memory to be used as ordinary E820_RAM
by the kdump kernel.
This also reverts what exactusablemap is all about:
Keep all reserved memory ranges of the original BIOS map.

Above would again wrongly remove the mmconf and other reserved regions
if kexec passes memmap=exactuseablemap,x@y

>From what I can see the patch looks fine, but above part should
simply be left out.

   Thomas
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