Re: 2MB page PV guest support clarification

[Mick Jordan <Mick.Jordan@sun.com>]

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On 02/27/09 16:03, Ian Pratt wrote:
>>> I found some posts from quite a while ago on xen-devel discussing
>>> patches to allow large pages, so my question is for clarification  on
>>> the status of this feature. I.e., is it in any stable release and if
>>> so what version?
>>>       
>> Its a work in progress, but there's nothing usable yet, as far as I
>> know.
>>     
>
> Oracle have been working on PV 2MB page support, and I expect they'll pitch in with an update.
>
> Over the last 18 months or so there have been a number of changes to xen's PV PT handling that make support of 2MB pages significantly easier than it was previously. However, the guest has to be careful how it uses them as it can't alias any memory that may be used for storing pagetables pages (that must be RO).
>
>   
Thanks for the update. I'll wait to hear from the Oracle guys.

You remark about aliasing prompts me to ask a general question about 
that. I am currently mapping physical to virtual 1-1 (because that is 
what minis-os has always done) as well as mapping parts of that to other 
areas in virtual memory. Both of these are RW mappings. Is that ok? It 
perfectly possible for me to unmap the 1-1 mappings or make them RO if I 
have to.

Mick


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