[coreboot] memtest86+ test fails at 3070.7MB

[Jonathan A. Kollasch]

On Thu, Aug 20, 2015 at 06:36:00PM +0800, Iru Cai wrote:
> Hi,
> 
> I installed coreboot(4.1-315-gf58746b) on a ThinkPad X220, with factory VGA
> option ROM and SeaBIOS 1.7.5 as payload. When I run memtest86+ on this
> machine, it reports a fail at 3070.7MB. If I just install a 2GB memory
> module, it passes the test. So what makes memtest86+ give a test failure?

Any other differences, particularly with respect to attached USB devices
between each test?

If you run memtest86+ on SeaBIOS w/ USB (or other DMA-using hardware)
on coreboot, you can expect to see memory test failures due to DMA
clobbering the memory you're trying to test.  You need a memtest86+
patched to not check for a coreboot/linuxbios memory map.  SeaBIOS
reserves its own memory in the BIOS memory map, but not the coreboot
memory map, so when running SeaBIOS the coreboot memory map is wrong.

	Jonathan Kollasch