Re: Windows side agrees that lowmem corruption is a problem too

From: Robert Hancock
Date: Thu Jun 10 2010 - 21:15:33 EST

On 06/08/2010 02:31 PM, H. Peter Anvin wrote:
On 06/08/2010 12:22 PM, Ondrej Zary wrote:

Yep, patterns of some silly OSD bitmap showed up in one of the corruption -
firmware displaying a 'you inserted a cable' kind of icon somewhere and
messing up the SMM code or so ...

I agree that dis-using<1M by default is probably the sanest option.

But please limit it to newer systems only (DMI present&& year> 200?). There
are many old machines running fine. Losing 1MB from 16MB is a bad thing.

Disusing 64K is something we can do unconditionally (especially since
we're only talking about 60K -- 15 pages -- of actually usable memory

Dropping all the low 0.6 MB (which is what it really is) is probably
unacceptable by default, but perhaps it makes sense to use it only for
ZONE_DMA or something.

According to the document, "Neither Windows Vista nor Windows 7 stores operating system code and data in the lowest 1 MB of physical memory, regardless of whether Windows is running on real or virtualized hardware", so doing the same in general might not be a bad thing (unless we have less than a certain amount of RAM).

They're also checksumming the low 1MB and writing an event log entry if corruption is detected after sleep events, so if WHQL tests start checking for that, maybe these bugs will start going away on new machines. Of course, on some machines the corruption apparently happens other times as well, so who knows..
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