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Re: [Qemu-devel] [PATCH 0/2] i386: "unavailable-features" QOM property
From: |
Jiri Denemark |
Subject: |
Re: [Qemu-devel] [PATCH 0/2] i386: "unavailable-features" QOM property |
Date: |
Wed, 22 May 2019 10:27:41 +0200 |
User-agent: |
Mutt/1.11.4 (2019-03-13) |
On Fri, May 10, 2019 at 17:32:03 -0300, Eduardo Habkost wrote:
> On Thu, May 09, 2019 at 06:36:18PM +0200, Jiri Denemark wrote:
> > On Thu, May 09, 2019 at 18:06:03 +0200, Igor Mammedov wrote:
> > > On Thu, 9 May 2019 10:56:17 -0300
> > > Eduardo Habkost <address@hidden> wrote:
> > >
> > > > On Thu, May 09, 2019 at 03:35:37PM +0200, Jiri Denemark wrote:
> > > > > Would this unavailable-features property contain only canonical names
> > > > > of
> > > > > the features or all possible aliases of all features? For example,
> > > > > "tsc-adjust" can also be spelled as "tsc_adjust". When calling
> > > > > query-cpu-model-expansion, we have a way to request all variants by
> > > > > running full expansion on the result of a previous static expansion.
> > > > > Can
> > > > > we get something like this for unavailable-features too?
> > > >
> > > > I'd like to avoid that, and refer only to the canonical names.
> > >
> > > Can we deprecate aliases to avoid confusion in future?
> > > (there aren't that many of them that used pre-QOM name format)
> >
> > If you come up with a way libvirt could use to detect which name it
> > should use when talking to QEMU...
>
> The property names are part of the API, and deprecation would
> just be documented in the QEMU documentation. Why would you need
> to enumerate them dynamically at runtime?
The tricky part is to know which variant of a particular feature name we
should use when talking to a specific version of QEMU. But I guess we
can use the new "unavailable-features" property for this purpose. When
the property is present, we can translate all feature names to their
canonical names (via a static translation table in libvirt). We'd be
using the old untranslated names when talking to any QEMU which does not
support the "unavailable-features" property.
But I hope we won't get into a situation when some CPU feature needs to
be renamed again, that would make a big mess.
Jirka
Re: [Qemu-devel] [PATCH 0/2] i386: "unavailable-features" QOM property, Igor Mammedov, 2019/05/09