Re: [Xen-devel] Re: [PATCH] qemu-xen: Fix PV segfault

[Kevin Wolf <kwolf@xxxxxxx>]

Gerd Hoffmann schrieb:
> Kevin Wolf wrote:
>> Actually, I think Xen PV is a different architecture, not just a
>> different PC machine.
> 
> That isn't visible to qemu though as cpu virtualization is handled by
> the xen hypervisor.
> 
>> So to be consistent with qemu it would be a
>> separate binary like qemu-system-xenpv.
> 
> I wouldn't do it that way for the reason outlined above, but it is an
> option, yes.

It's not only the CPU virtualization I'm talking about. PV machines also
have "hardware" devices completely different from PCs. Just look at
pc_init1(), that's all stuff PV machines won't need.

Concerning the CPU, I think of it as an architecture which is only
usable through an accelerator. Certainly it would be possible to do a
normal qemu emulation for this architecture, it just wouldn't make too
much sense.

>> HVM on the other hand would be more of an accelerator for the existing
>> x86 system emulation, just like kqemu or KVM.
> 
> Yep, sort of.  And some plumbing for xenbus for guests with pv-on-hvm
> drivers installed.
> 
> Glauber Costa is working on a nice abstraction layer for qemu
> accelerators btw.  Intention is to get kvm upstream merged.  It should
> also make it easier to get xen hvm support merged upstream.

Yes, I'm aware of his patches. That's actually why I used the term
"accelerator".

Kevin

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