[coreboot] memtest86 reading 0k memory

Kevin O'Connor kevin at koconnor.net
Thu Feb 19 16:43:44 CET 2015


On Wed, Feb 18, 2015 at 10:26:21PM +0100, Stefan Reinauer wrote:
> * Timothy Pearson <tpearson at raptorengineeringinc.com> [150205 19:23]:
> > e820: BIOS-provided physical RAM map:
> > BIOS-e820: [mem 0x0000000000000000-0x000000000009fbff] usable
> > BIOS-e820: [mem 0x000000000009fc00-0x000000000009ffff] reserved
> > BIOS-e820: [mem 0x00000000000f0000-0x00000000000fffff] reserved
> > BIOS-e820: [mem 0x0000000000100000-0x000000003ffacfff] usable
> > BIOS-e820: [mem 0x000000003ffad000-0x000000003fffffff] reserved
> > BIOS-e820: [mem 0x00000000e0000000-0x00000000efffffff] reserved
>  
> One of the issues seems to be that the coreboot table space is not
> marked as reserved (i.e. the lower 4k should be marked as reserved, and
> whatever is used at the top of memory)

coreboot tends to reserve the first 4K, but this breaks lots of
bootloaders.  So, SeaBIOS always overrides coreboot and unreserves the
first 4K.  My experience is that the first one megabyte of the e820 is
just "magical" and should always read as listed above.

Separately, it is possible for SeaBIOS to remove the coreboot table
forwarder, and thus force memtest86 to not use the coreboot tables.
I'm not sure if this would affect other programs though.

-Kevin



More information about the coreboot mailing list