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

Robert Hancock
2007-05-31T14:27:38Z

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
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