Re: [Xen-devel] x86-64's contig_initmem_init

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 30 Aug 2005, at 15:07, Keir Fraser wrote:

> The tail part of the initial mapping has no special handling on i386 
> nor on x86_64. It just gets freed up when we free from 0 up to 
> max_pfn, and it never gets reserved (the reserved region precisely 
> covers kernel text/data and initial page tables).
> Actually, that could be another bug on x86/64 -- I may need to 
> truncate the initial mapping, or we may be ending up with spurious 
> extra writable mappings to some pages... I'll take a look and see if 
> this is the case.
Okay, I see what you mean. init_memory_mapping() sets start_pfn to 
something after the domain-builder-provided mapping. So we probably 
lose around 4MB of RAM per domain on x86/64.... that'll have to be 
fixed. I didn't originally write this code, btw. ;-)
i386 does not have this concept of an initial/kernel mapping separate 
from the 1:1 mapping of all phys mem. So this particular problem cannot 
occur.
 -- Keir


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