Re: More E820 brokenness

From: Jordan Crouse
Date: Thu Sep 27 2007 - 18:33:40 EST

On 27/09/07 15:17 -0700, H. Peter Anvin wrote:
> As luck would have it, it's not just an obscure Geode system which has a
> broken E820 implementation. Today I received a bug report about a Dell
> system (XPS M1330) with broken E820.
> Unfortunately, the workaround for the Geode breaks this system, because
> x86-64 doesn't fall back to the e801/88 information like the i386 kernel
> does.
> I wonder if the relevant people could test out this patch to see how it
> works on their respective system. This patch reverts to 2.6.23-rc8
> behaviour of simply truncating the map, but still makes e801/88 info
> available to the kernel; this hopefully should match 2.6.22 behaviour.

Breaks on the Geode - original behavior.

I think that having boot_prams.e820_entries != 0 makes the kernel
assume the e820 data is correct.

> I want to emphasize that this is seriously broken. Using a partial e820
> map could have disastrous results, since the kernel will have partial
> memory map information and not know about reserved areas, etc. Part of
> me feels that the right thing to do is what the current git kernel does
> -- either fall back to e801, or stop and error.

I'm inclined to agree.


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