[syslinux] isolinux problem since 3.74

[H. Peter Anvin]

On 10/14/2009 01:26 PM, Stillwell, Bryan wrote:
> On Tue, 2009-10-13 at 23:41 +0000, H. Peter Anvin wrote:
>> Either way, the mostly likely problem isn't gPXE but rather memory line
>> number 6, which is marked "usable" (type 1) but has the flag bits [9].
>> The value 9 is AddressRangeSlowAccess which was only defined in the ACPI
>> 4.0 specification -- it's likely that something is just severely *weird*
>> with your system.
> 
> Here's the memory map when booting from isolinux.  You're right that
> it's different from the one that was loaded with pxelinux+gPXE.
> 
> You mentioned value 9 is AddressRangeSlowAccess, but looking at the 4.0
> spec, it appears to be AddressRangeErrorLog instead.  That doesn't seem
> like something that should be marked as usable, so I'm looking into it.
> 

You're right, my bad.

> BTW, I tried booting with pxelinux 3.75 and the same config files the CD
> uses, and it works fine.  Maybe all those zero entries which are seen
> when booting off the CD are causing the problem?  I've been told the
> Linux kernel ignores them.

The Linux kernel should ignore them, as should Syslinux, but there is of
course always the possibility there is a bug.

The 3.74 or older Syslinux doesn't attempt to use non-contiguous chunks
of high memory at all.  3.75 and higher *does*, because machines have
started appearing with memory holes in the lower part of high memory --
again.

	-hpa