Re: [PATCH] linux/x86: Initialize high_memory as early as possible

["Jan Beulich" <jbeulich@novell.com>]

>>> Keir Fraser <Keir.Fraser@cl.cam.ac.uk> 29.06.06 15:55 >>>
>
>On 29 Jun 2006, at 14:42, Jan Beulich wrote:
>
>> Also all other variables dependent on the same input(s). This is a 
>> prerequisite patch for two ones to follow. I will
>> post a similar change for mainline Linux soon.
>>
>> Signed-off-by: jbeulich@novell.com 
>
>Is this just for the usage in kunmap_atomic? Why did you change that, 

Not only, also for the added check in xen_{create,destroy}_contiguous_region
in another of the patches just sent.

>by the way: FIXADDR_START looked like a safe enough test to me.

This didn't seem safe enough to me, and apparently also not to the original
author (at least I attribute the FIXME comment to this) - after all not
everything before FIXADDR_START is high memory.
One could say that under DEBUG_HIGHMEM the check should be more strict
(so that the subsequent BUG() condition fires in more broken cases), but
without DEBUG_HIGHMEM it might be left as-is to avoid zapping incorrect
page table entries.

Jan