Re: [Xen-devel] [Minios-devel] [PATCH v4 0/<VARIOUS>] Begin to disentangle libxenctrl and provide some stable libraries

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Thu, 2015-11-19 at 16:20 +0000, Stefano Stabellini wrote:
> 
> > I think having three or four functions in libxendevicemodel which offer
> > these exact facilities while retaining the underlying (possibly more
> > flexible) functionality in libxenctrl for other users (dombuilder, other in
> > tree tools) would be tolerable.
[...]
> The main question would then be whether libxendevicemodel should wrap
> > libxenctrl in a stable layer or whether it should actually duplicate the
> > functionality in the thin wrappers.
> 
> Couldn't we rename the existing libxc calls and make them stable?

This was sort of what I was getting at a couple of paras earlier (quotes
trimmed to just that bit).Â

The current functions are far more flexible than what QEMU requires (and
that flexibility is used by in tree components). ÂI'm not sure we can (or
want to) declare the full breadth of the functionality of e.g.
xc_domain_add_to_physmap and xc_domain_pin_memory_cacheattr as being stable
and it would be much easier to arrive at and agree on a suitable stable
interface for more limited specific functionality.

If we were to just say "xc_domain_add_to_physmap and
xc_domain_pin_memory_cacheattr are now stable" then having them in a
libxendevicemodel would be incorrect, since they are not in any way
specific to device models.


> ÂÂKeep
> in mind that we already have stable wrappers in QEMU in
> include/hw/xen/xen_common.h. I don't think we need two layers of
> wrappers :-)

Indeed, but part of the purpose of Xen providing stable libraries is that
external components/users should not need wrappers.

IOW IMHO the current wrappers in QEMU should, as part of this exercise in
providing stable interfaces, be deprecated and remain only to retain
compatibility with older versions of Xen which lacked the stable
interfaces, with a view to them eventually being removed as support for
those older Xen's is removed from QEMU.

Ian.

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