linux-kernel - Re: Use of memmap= to forcibly recover memory in 3GB-4GB range

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Message-ID: <CAE9FiQUPBGi8kQ2bA2mdWz_gO1R9UmM-QdWXzEfTh6K0i+ZkGg@mail.gmail.com>
Date:	Tue, 15 Jan 2013 23:02:29 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Alex Villacís Lasso <a_villacis@...osanto.com>,
	linux-kernel@...r.kernel.org
Subject: Re: Use of memmap= to forcibly recover memory in 3GB-4GB range - is
 this safe?

On Tue, Jan 15, 2013 at 6:28 PM, H. Peter Anvin <hpa@...or.com> wrote:
> On 01/15/2013 05:47 PM, Alex Villacís Lasso wrote:

>> 2) I have recompiled the kernel to support the memtest parameter. When
>> using it, the extra memory segment appears to be as healthy as other
>> areas of memory. However this might only mean that it is wrapping into
>> healthy low RAM.

memtest should print out about the range.

and if you are using 64bit kernel, it should test all memory
except for range with kernel itself.


>>
>> Is my reasoning sane? Is there a way to know, once and for all, whether
>> the extra "memory" is real and safe to use or not?
>
>
> Maybe you can get memtest86+ to test this phantom memory?  But yes, it does
> sound like a BIOS bug.

that may not help, because e820 from bios is not right.

Yinghai
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