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Re: Guest-visible phys2mach part of Xen arch-neutral API? was: [Xen-devel] Uses of &frame_table[xfn]

  • To: "Hollis Blanchard" <hollisb@xxxxxxxxxx>
  • From: "Magenheimer, Dan (HP Labs Fort Collins)" <dan.magenheimer@xxxxxx>
  • Date: Wed, 4 Jan 2006 07:21:51 -0800
  • Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxx>
  • Delivery-date: Wed, 04 Jan 2006 15:26:59 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xensource.com>
  • Thread-index: AcYRQpaGxfGpFZQZQKCkBhgTssnNIA==
  • Thread-topic: Re: Guest-visible phys2mach part of Xen arch-neutral API? was: [Xen-devel] Uses of &frame_table[xfn]

Has Xen/ppc tried to implement the Xen balloon or network
drivers yet?  There appear to be a lot of dependencies
in there on a guest-aware p2m table.


>From: Hollis Blanchard <hollisb@xxxxxxxxxx>
Subject: Re: Guest-visible phys2mach part of Xen arch-neutral API?
        was:    [Xen-devel] Uses of &frame_table[xfn]
To: xen-devel@xxxxxxxxxxxxxxxxxxx
Cc: Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
Message-ID: <200601031555.20229.hollisb@xxxxxxxxxx>
Content-Type: text/plain;  charset="iso-8859-1"

On Friday 30 December 2005 13:50, Magenheimer, Dan (HP Labs Fort
> I think there are two critical questions that are very highly
> related.  To me, the critical question is how many changes
> to a guest are required to run on Xen.  I've argued for a long
> time that paravirtualization changes should be minimized/optimized
> to only those that are absolutely necessary for functionality
> and performance.   DMA-capable domains require either p==m
> or non-trivial changes to the guest.  On x86, non-trivial changes
> to the guest are necessary anyway due to the x86 memory architecture
> so p!=m comes "for free".  This is not necessarily the case
> for non-x86 Xen machines.

For the record, the PowerPC port is not currently using a p2m table in
(or any domain for that matter). We are still using the PAPR interface
enterprise hypervisor ABI) for memory management.

Using Xen terminology, that interface says that domains pass only
addresses to the hypervisor, and the hypervisor performs the physical to

machine translation.

I think we're not looking to diverge from this interface unless we
have to, and so far (given the maturity of the PPC port) we haven't had

Hollis Blanchard
IBM Linux Technology Center

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