linux-kernel - Re: Windows side agrees that lowmem corruption is a problem too

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Date:	Tue, 08 Jun 2010 14:57:53 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
CC:	Ondrej Zary <linux@...nbow-software.org>,
	Ingo Molnar <mingo@...e.hu>,
	Yuhong Bao <yuhongbao_386@...mail.com>,
	linux-kernel@...r.kernel.org, gregkh@...e.de
Subject: Re: Windows side agrees that lowmem corruption is a problem too

On 06/08/2010 02:56 PM, Alan Cox wrote:
>>> I agree that dis-using <1M by default is probably the sanest option.
>>
>> But please limit it to newer systems only (DMI present && year > 200?). There 
>> are many old machines running fine. Losing 1MB from 16MB is a bad thing.
> 
> Losing the low 1MB is bad thing anyway for things like firmware flashing
> and other weird crap that needs low pages (floppy controllers etc).
> 
> Losing 64K (but reporting corruption in it in a big scary way) is
> probably sensible for distributions, but its a config item so its policy
> so that wouldn't be a problem.
> 
> It has to be painful to the vendors so they get complaints, reports and
> support call costs. Otherwise they won't have the correct incentives to
> fix their mess.

We have already functionally lost 64K on all existing machines... I
think the current blacklist covers 90% or more of all systems in
existence, and we keep filling in the few holes that remain.

Adding the remaining half-megabyte of RAM really shouldn't be done
unconditionally, but as I said it could plausibly be reserved for
ZONE_DMA only.

	-hpa

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