Re: [PATCH] abstract out bits of ldt.c

[Zachary Amsden]

Chris Wright wrote:

> * Zachary Amsden (zach@xxxxxxxxxx) wrote:
>  
>
> > Does Xen assume page aligned descriptor tables?  I assume from this 
> >    
>
> Yes.
>
>  
>
> > patch and snippets I have gathered from others, that is a yes, and other 
> > things here imply that DT pages are not shadowed.  If so, Xen itself 
> > must have live segments in the GDT pages, so how do you allocate space 
> > for the per-CPU GDT pages on SMP?
> >    
>
> early during boot.
>  

Doesn't that require 16 pages per CPU?  That seems excessive to impose 
on a native build.  Perhaps we could get away with 1 page per CPU for 
the GDT on native boots and bump that up to 16 if compiling for a 
virtualized sub-architecture - i.e. move GDT to a page aligned struct 
for native (doesn't cost too much), and give it MACH_GDT_PAGES of space 
which is defined by the sub-architecture.

Let's take this thread over to virtualization@xxxxxxxxxxxxxx as well.

Zach
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