Re: Bisected regression (Was Re: current -git fails to boot on nehalem-ex)

H. Peter Anvin
2009-12-10T22:55:21Z

On 12/10/2009 02:45 PM, Yinghai Lu wrote:
> H. Peter Anvin wrote:
>> On 12/10/2009 01:07 PM, Yinghai Lu wrote:
>>> it turns out BIOS is using first 64k for mptable without reserve it.
>>>
>>> so try to find good range for it instead of hard code it.
>>> in case some bios try to use that range for sth.
>>>
>>
>> Is this an EFI BIOS? Otherwise, the first 64K would be clobbered anyway
>> by the boot loader, so it is invalid anyway... If it is EFI, it is
>> theoretically possible.
>
> Jens said acpi=off works with 2.6.32.
>
> can you specify the exact byte position that boot loader could touched?
>

A legacy-BIOS boot loader will typically clobber all memory from 0x600
(in theory 0x501) up to the FBM point; a pointer to the FBM mark is
given by (*(uint16_t *)0x413) << 10.

-hpa