Re: Case: 7454422: Re: Kernel 2.6.21.3 does not work with 8GB of RAM on Intel 965WH motherboards. (FULL DMESG)

[Robert Hancock <hancockr@shaw.ca>]

Justin Piszcz wrote:
> On Thu, 31 May 2007, Parag Warudkar wrote:
>
> > Robert Hancock wrote:
> > > I think that mem=8832M would work as well, to make the kernel use 
> > > only the memory that is marked cacheable. (It looks like this 
> > > parameter takes the highest memory address we want the kernel to use, 
> > > not the highest memory amount.)
> > Yep, and that would be much easier too.
> >
> > I am curious though as this seems to be somewhat common a problem, 
> > could we make the kernel analyze which memory is not cacheable (it 
> > already knows this via MTRR) and not use that portion for anything? 
> > Plus may be warn the user to contact their BIOS vendor to correct the 
> > problem?
> >
> > I think that would be possible - even if the kernel knows late that 
> > the memory was uncached we could migrate those pages in that region to 
> > someplace else?
> >
> > Parag
>
> That is an excellent question and I wonder the same thing.  I also had 
> this problem when I only used 4GB of ram and upgraded the (another 
> motherboard, I have two) past version 1666P and I had no idea what was 
> going on other than the BIOS did not work correctly.
>
> In this case however it worked with 4GB with bios version 1612P but not 
> with 8GB.  Is this the case of a buggy BIOS for the 965 chipset or do 
> Intel boards have a lot of issues?

We could conceivably generate a warning if the MTRRs don't map all of 
the physical memory as write-back. Actually, conceivably we could 
actually go and fix up the MTRRs if we found them to be wrong according 
to the E820 memory map. That would be more complicated, however.

--
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@nospamshaw.ca
Home Page: http://www.roberthancock.com/

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