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SubjectRe: [PATCH]Fix broken VMI in 2.6.27-rc..


On Thu, 7 Aug 2008, H. Peter Anvin wrote:
>
> Just moving it down by 4 MB doesn't help, since the VMI guys want as much as
> 64 MB, which is half the standard vmalloc area and hence too much address
> space lost. We can't put it at the bottom of the vmalloc area, since that
> boundary is not fixed, either.

Yeah, ok. Since this is a 32-bit only issue, 64MB is actually a fair chunk
of our already limited virtual space.

> The one remaining fixed boundary in the machine is the kernel-userspace
> boundary. Hence moving the 1:1 area up by one PDE unit and sticking the
> fixmap area in that region.

Yeah, ok, but I'd be more nervous about the validation issues there. There
might be a lot of code that assumes that TASK_SIZE is the start of the 1:1
area. It does sound like a good approach, it just makes me worry about the
test coverage.

Linus


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