[libvirt] [PATCH] libxl: detect support for save and restore
Daniel P. Berrange
berrange at redhat.com
Thu Jun 26 09:35:44 UTC 2014
On Wed, Jun 25, 2014 at 01:10:20PM -0600, Eric Blake wrote:
> On 06/25/2014 12:13 PM, Jim Fehlig wrote:
> > libxl does not support save, restore, or migrate on all architectures,
> > notably ARM. Detect whether libxl supports these operations using
> > LIBXL_HAVE_NO_SUSPEND_RESUME. If not supported, drop advertisement of
> > <migration_features>.
> >
> > Found by Ian Campbell while improving Xen's OSSTEST infrastructure
> >
> > http://lists.xen.org/archives/html/xen-devel/2014-06/msg02171.html
> > Signed-off-by: Jim Fehlig <jfehlig at suse.com>
> > ---
> >
> > Derived from a test patch I sent to Ian Campbell
> >
> > http://lists.xen.org/archives/html/xen-devel/2014-06/msg03150.html
> >
> > Includes fixups Ian provided later in the thread.
> >
> > src/libxl/libxl_conf.c | 4 ++++
> > src/libxl/libxl_driver.c | 8 ++++++++
> > 2 files changed, 12 insertions(+)
>
> >
> > +#ifndef LIBXL_HAVE_NO_SUSPEND_RESUME
>
> Double negative logic is hard to read. Oh well.
>
>
> >
> > static virDriver libxlDriver = {
> > @@ -4594,10 +4598,12 @@ static virDriver libxlDriver = {
> > .domainSetMemoryFlags = libxlDomainSetMemoryFlags, /* 0.9.0 */
> > .domainGetInfo = libxlDomainGetInfo, /* 0.9.0 */
> > .domainGetState = libxlDomainGetState, /* 0.9.2 */
> > +#ifndef LIBXL_HAVE_NO_SUSPEND_RESUME
> > .domainSave = libxlDomainSave, /* 0.9.2 */
> > .domainSaveFlags = libxlDomainSaveFlags, /* 0.9.4 */
> > .domainRestore = libxlDomainRestore, /* 0.9.2 */
> > .domainRestoreFlags = libxlDomainRestoreFlags, /* 0.9.4 */
> > +#endif
>
> Hmm - do we do conditional registration in any other driver based on
> configure-time results? I'd almost rather always provide the driver
> registration, and then use #ifdefs in the body of that function to
> either provide a sane result or else report that the compilation
> environment was too old, rather than omit the support altogether. Maybe
> get Dan's opinion on this?
I think it'd end up pretty much the same in both cases since we'd
end up using VIR_ERR_NO_SUPPORT in both cases. The argument in
favour of providing the driver registration and #ifdef in the
impl is that you could give a slightly more precise error report.
eg instead of "This function isn't supported" you could say
"This function isn't supported on this architecture/version",
but that's pretty much the only difference you'd get.
Regards,
Daniel
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