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

["H. Peter Anvin" <hpa@kernel.org>]

Linus Torvalds wrote:
> 
> 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.
> 

Indeed.  Unfortunately I don't see any other options.

	-hpa