Re: Possible PCI subsystem bug in 2.4

From: Eric W. Biederman (ebiederm@xmission.com)
Date: Fri May 04 2001 - 10:41:51 EST


Alan Cox <alan@lxorguk.ukuu.org.uk> writes:

> > I suspect it would be safe to round up to the next megabyte, possibly up
> > to 64MB or so. But much more would make me nervous.
> > Any suggestions?
>
> I'd go for 1MByte simply because I've not seen an EBDA/NVRAM area that large
> stuck at the top of RAM. 1Mb would fix the Dell. (It was only when I saw
> your email it suddenely clicked and I grabbed the bootup log)

There are a couple of options here.
1) read the MTRRs unless the BIOS is braindead it will set up that area as
   write-back. At any rate we shouldn't ever try to allocate a pci region
   that is write-back cached.

2) read the memory locations from the northbridge. It's not possible
   on every chipset (lack of documentation) but with the linuxBIOS
   project we code for a couple of them, and we are working on more
   all of the time.

Eric

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