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Re: [Xen-devel] Essay on an important Xen decision (long)

To: Mark Williamson <mark.williamson@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] Essay on an important Xen decision (long)
From: Hollis Blanchard <hollisb@xxxxxxxxxx>
Date: Wed, 11 Jan 2006 15:16:35 -0600
Cc: "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxx
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On Wed, 2006-01-11 at 16:22 +0000, Mark Williamson wrote:
> IIRC, PPC also performs P-to-M translations in the hypervisor, but I vaguely 
> recall that happening during an explicit pagetable update hypercall - kind of 
> a middle road between the x86 and IA64 approaches...  Some PPC guy may jump 
> in and correct me at this point, though ;-)

It's pretty simple: for Xen/x86, the kernel does translation and the
hypervisor does validation. For PAPR on PPC hardware, the hypervisor
does both translation and validation.

This is done for every mapping hcall: the domain makes an hcall to map
physical address P, and the hypervisor translates to machine address M
and allows or rejects the request.

Page fault exceptions are delivered by the processor to the domain (not
the hypervisor), which reacts by making a mapping hcall.

Hollis Blanchard
IBM Linux Technology Center

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