[coreboot] memtest86 reading 0k memory

[Aaron Durbin]

On Thu, Feb 5, 2015 at 12:48 PM, Timothy Pearson
<tpearson at raptorengineeringinc.com> wrote:
> On 02/05/2015 12:38 PM, Jonathan A. Kollasch wrote:
>>
>> That's a pretty old memtest86+.  Also, memtest86+ prefers
>> linuxbios/coreboot memory map to e820.  This becomes a problem
>> when SeaBIOS sets up a USB controller to DMA to e820-reserved
>> memory that wasn't reserved by coreboot.
>>
>> Try a modern memtest86+ with the coreboot table probe patched out.
>>
>>         Jonathan Kollasch
>
>
> Yep, that was it.  Didn't catch the obsolete version number.
>
> I'm trying to figure out the point of memtest86 reading the coreboot tables.
> It doesn't help that the coreboot tables / e820 map are apparently wrong;
> memtest86+ almost immediately started stepping on the lower MMIO regions
> (e.g. 0xb800) rendering the display mostly useless. Interestingly Linux
> doesn't seem to have any problems; I'll need to investigate further.
>

Your e820 looks fine to me. memtest86 should just be testing the
usable regions. Since b800 isn't in there, the only issue that could
arise is it using that physical address as a mmio bar. However, that'd
be an OS level thing, and I wouldn't expect the memtest86 doing any
such things. It sounds more like it does a merge of some sort with
e820 and its notion of valid memory instead relying on e820 proper.

> --
> Timothy Pearson
> Raptor Engineering
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> http://www.raptorengineeringinc.com
>
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