Xen devel - Jan 2006 - PSE support in VT guests

As far as I can tell, Xen''s approach to PSE support in VT guests is it
just doesn''t expose the feature.  Is there any plan on adding support
for it?  Or is it already there and I am just missing something?

thanks

later
sdg

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On 13 Jan 2006, at 19:26, Stephen Goglin wrote:
> As far as I can tell, Xen''s approach to PSE support in VT guests
is it
> just doesn''t expose the feature.  Is there any plan on adding
support
> for it?  Or is it already there and I am just missing something?
I think it''s there already. After all, 64-bit OSes know the CPU will 
always support PSE.

  -- Keir


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Keir Fraser wrote:
> On 13 Jan 2006, at 19:26, Stephen Goglin wrote:
> 
>> As far as I can tell, Xen''s approach to PSE support in VT
guests is
>> it just doesn''t expose the feature.  Is there any plan on
adding
>> support for it?  Or is it already there and I am just missing
>> something? 
> 
> I think it''s there already. After all, 64-bit OSes know the CPU
will
> always support PSE.
> 
>   -- Keir
> 
That''s correct. For 32-bit guests, we simply disable PSE at the CPUID
instruction. It''s possible to turn it on (by extending the PSE
supporting code for 64-bit), but the current implementation of 2MB page
support is to fracture it into 4KB pages in the shadow page table, as we
don''t have a generic 2MB page allocator in Xen (yet?). So in terms of
performance, we don''t gain anything even if we enable PSE for 32-bit
guests.

Jun
---
Intel Open Source Technology Center

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