Re: [Xen-devel] [PATCH 1/5] xen/arm: implement do_hvm_op for ARM

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Tue, 2012-06-26 at 19:29 +0100, Stefano Stabellini wrote:
> On Tue, 26 Jun 2012, Ian Campbell wrote:
> > We need to device how hybrid our hybrid arm guests are going to be.
> 
> Right.
> 
> 
> > The particular hvm params you are using here (evtchn port etc) typically
> > live in start_info for a PV guest. In principal we could define a start
> > info for ARM too but that leaves the question of how the guest can find
> > it (which loops up back to hvm_params...).
> 
> One way would be to introduce a new XENMAPSPACE, like we have done for
> XENMAPSPACE_shared_info. Then the guest would use a
> XENMEM_add_to_physmap to map it.
> 
> 
> > Looking at the other stuff in start_info, it has stuff like modules (aka
> > ramdisks) and command lines which ARM guest get via the normal ARM boot
> > protocol stuff (i.e. the domain builder does it) and a bunch of stuff
> > which seems to only make sense for proper-PV guests.
> > 
> > So maybe HVM PARAM is the right answer?
> 
> Yes, that is one of the reasons why I preferred introducing hvm_op
> rather than a new XENMAPSPACE: we don't need anything else from
> start_info aside from the parameters already provided through
> HVMOP_get_param.
> On the other hand hvm_op can be useful for other things, for example one
> day we might use the HVM_PARAM_IOREQ_PFN parameter.

That would be in future if/when we support proper "HVM" (or "PVHVM") ARM
guests i.e. ones which appear to the guest like a particular physical
platform, rather than our virtual hybrid platform, and therefore have a
QEMU providing a DM for that hardware?

> Most importantly, from the Linux side of things, acting like a PV on HVM
> kernel is a perfect fit, the changes required are down to a minimum.

OK.

> > sinfo does have flags which contains stuff like SIF_INITIAL_DOMAIN.
> > Might we want that?
> 
> We don't need it thanks to XENFEAT_dom0, see 
> 1340381685-22529-3-git-send-email-stefano.stabellini@xxxxxxxxxxxxx

Great.



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