linux-kernel - Re: [RFC PATCH 3/3] x86, boot: Change the BIOS corruption checker to scan 640K

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Date:	Mon, 11 Nov 2013 23:19:30 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Ingo Molnar <mingo@...nel.org>
CC:	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Olof Johansson <olof@...om.net>
Subject: Re: [RFC PATCH 3/3] x86, boot: Change the BIOS corruption checker
 to scan 640K

On 11/11/2013 08:07 PM, Ingo Molnar wrote:
> I agree with your patches so far, and I'd suggest we go even further: I'd 
> say the config option is now a misnomer, it should probably be renamed to 
> CONFIG_X86_FORCE_RESERVE_BIOS_LOW_1MB=y or so.

Why is that?  It doesn't seem to make much sense to me.  I think the
current option names seem to be just fine, but perhaps I'm missing
something.

> Btw., should we also force-reserve the remaining bits over 640K..1MB, if 
> they are not marked as reserved in the memory maps, or do we already 
> force-reserve them somewhere?

We do, in trim_bios_range().  We treat it as available for I/O
assignments, since that is necessary on some systems.

> The CONFIG_X86_BOOTPARAM_MEMORY_CORRUPTION_CHECK=y option and the 
> memory_corruption_check=1 boot option then allow the activation of the low 
> memory corrupion checker - which debug facility can be used on systems 
> where someone wants to live dangerously and not reserve the low 1MB of RAM 
> to the firmware.

That is indeed what this patch does, I think...

	-hpa


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