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    |   xen-ia64-devel
RE: [Xen-devel] Review needed for	"commonisation"ofcommon/grant_table.c 
| To: | "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>,	"Tian, Kevin" <kevin.tian@xxxxxxxxx>, <cwc22@xxxxxxxxx> |  
| Subject: | RE: [Xen-devel] Review needed for	"commonisation"ofcommon/grant_table.c |  
| From: | "Dong, Eddie" <eddie.dong@xxxxxxxxx> |  
| Date: | Tue, 14 Jun 2005 11:01:48 +0800 |  
| Cc: | xen-devel@xxxxxxxxxxxxxxxxxxx, xen-ia64-devel@xxxxxxxxxxxxxxxxxxx |  
| Delivery-date: | Tue, 14 Jun 2005 03:01:49 +0000 |  
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| Thread-index: | AcVuBlLakJ6ZKpDrS66Z9eBsen+ZAQAACwkgAAwg/8AAeuKgsAAA48NAAA2rMcAAC+ELEA== |  
| Thread-topic: | [Xen-devel] Review needed for	"commonisation"ofcommon/grant_table.c |  
| Magenheimer, Dan (HP Labs Fort Collins) wrote:
> 
> I understand (I think) how it works on x86.  But the memory
> model is somewhat different on ia64.  Domain 0 has access
> to all of machine memory and can create a duplicate mapping
> for any page of any unprivileged guest.  This is not controlled
> by Xen (in the current implementation). 
Doesn't XEN/domain0 use ballon driver to give memory to HV and 
let HV memory system allocate for other domains? Or are you proposing
a new XEN memory mechanism (can you share with us for the details 
so that we can be in same page if this is the case)? 
But anyway I don't think IA64 has such kind of specials.
> As long as a page
> is shared between Domain 0 and Domain N, I don't see that
> reference counts are necessary.
Don't you want to keep the capability for the code coming soon?
> 
> If pages are to be shared between two unprivileged domains,
> there may be some value in reference counts.  But that doesn't
> fit very well with the current frontend/backend model.
> 
Eddie
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