linux-kernel - Re: [PATCH] Hibernate: Do not assume the first e820 area to be RAM

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Date:	Tue, 12 Aug 2014 11:35:33 +0200
From:	Pavel Machek <pavel@....cz>
To:	"Lee, Chun-Yi" <joeyli.kernel@...il.com>
Cc:	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	Len Brown <len.brown@...el.com>, Takashi Iwai <tiwai@...e.de>,
	linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org,
	"Lee, Chun-Yi" <jlee@...e.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH] Hibernate: Do not assume the first e820 area to be RAM

On Mon 2014-08-11 18:50:52, Lee, Chun-Yi wrote:
> In arch/x86/kernel/setup.c::trim_bios_range(), the codes introduced
> by 1b5576e6 (base on d8a9e6a5), it updates the first 4Kb of memory
> to be E820_RESERVED region. That's because it's a BIOS owned area
> but generally not listed in the E820 table:
> 
> [    0.000000] e820: BIOS-provided physical RAM map:
> [    0.000000] BIOS-e820: [mem 0x0000000000000000-0x0000000000096fff] usable
> [    0.000000] BIOS-e820: [mem 0x0000000000097000-0x0000000000097fff] reserved
> ...
> [    0.000000] e820: update [mem 0x00000000-0x00000fff] usable ==> reserved
> [    0.000000] e820: remove [mem 0x000a0000-0x000fffff] usable
> 
> But the region of first 4Kb didn't register to nosave memory:
> 
> [    0.000000] PM: Registered nosave memory: [mem 0x00097000-0x00097fff]
> [    0.000000] PM: Registered nosave memory: [mem 0x000a0000-0x000fffff]
> 
> The codes in e820_mark_nosave_regions() assumes the first e820 area to be
> RAM, so it causes the first 4Kb E820_RESERVED region ignored when register
> to nosave. This patch removed assumption of the first e820 area.
> 
> Cc: "Rafael J. Wysocki" <rjw@...ysocki.net>
> Cc: Len Brown <len.brown@...el.com>

Acked-by: Pavel Machek <pavel@....cz>

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