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[Xen-ia64-devel] Re: [Xen-devel] [RFC] hvm-stub for ia64

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: [Xen-ia64-devel] Re: [Xen-devel] [RFC] hvm-stub for ia64
From: tgingold@xxxxxxx
Date: Thu, 22 Nov 2007 10:31:30 +0100
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Quoting Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>:

> Does the hvmstub have to look different to an hvm guest from the p.o.v. of
> the tools? It's rather a shame to introduce a third kind of domain at that
> level.
There are of course differences: qemu shouldn't be started.  And the builder
C function is different.  I can try to merge with the hvm builder function
but I am not sure it is worth.  The amount of new code is still rather small
for tools.

> How do you think this appraoch compares with a separate stub domain per HVM
> guest? That's the approach being developed on the x86 side, but it would be
> nice to not increase divergence between x86 and ia64.
I think my approach is much more simpler.  Just look at the amount of new code
for hypervisor and tools: very small.

There is nothing ia64 specific in hvmstub.  For performance, it requires
cheap virtual to physical (ie switching paging on and off) transitions in the
guest, but I think this is already true for x86.

The real work is in the stub firmware which could be partially shared between
x86 and ia64.  However I'd also like to implement more realistic machine
emulation for ia64 in order to be able to run more OSes.

Tristan.

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