PSE support in VT guests

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PSE support in VT guests

Stephen Goglin
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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Re: PSE support in VT guests

Keir Fraser

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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RE: PSE support in VT guests

Nakajima, Jun
In reply to this post by Stephen Goglin
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
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Intel Open Source Technology Center

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