Xen devel - Jun 2006 - [PATCH] linux/x86: Initialize high_memory as early as possible

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 



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

  -- Keir


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>>> 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

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On 29 Jun 2006, at 15:03, Jan Beulich wrote:
> 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.
Any kmap_atomic virtual address should be above FIXADDR_START. You have 
a point about debugging though (e.g., passing a non-atomic kmap address 
to kunmap_atomic).

  -- Keir


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