Re: [Xen-devel] [PATCH v5 08/24] libxl: introduce libxl__vnuma_config_check

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Feb 13, 2015 at 10:39:25AM -0500, Elena Ufimtseva wrote:
> On Fri, Feb 13, 2015 at 10:12 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> > On Fri, Feb 13, 2015 at 02:15:47PM +0000, Ian Jackson wrote:
> >> Wei Liu writes ("[PATCH v5 08/24] libxl: introduce 
> >> libxl__vnuma_config_check"):
> >> > This function is used to check whether vNUMA configuration (be it
> >> > auto-generated or supplied by user) is valid.
> >>
> >> This looks plausible, but I think you should explain what the impact
> >> of this patch is.  Presumably the intent is to replace various later
> >> failures with ERROR_FAIL with something more useful and more
> >> specific ?
> >>
> >
> > Yes, providing more useful error message is on aspect. Another aspect is
> > just to do sanity check -- passing an invalid layout to guest doesn't
> > make much sense.
> >
> >> Are there any cases which this new check forbids but which are
> >> currently accepted by libxl ?  If so then we have to think about
> >> compatibility.
> >>
> >
> > First thing is there is no previous supported vNUMA interface in
> > toolstack so there won't be a situation where previous good config
> > doesn't pass this check.
> >
> > Second thing is if user supplies a config without vNUMA configuration
> > this function will not get called, so it won't have any effect.
> >
> >> Also I would like to see an ack from the authors of the vnuma support,
> >> as I'm not familiar enough with vnuma to fully understand the
> >> semantics of the new checks.
> >>
> >
> > Elena and Dario, what do you think?
> 
> The checks themselves look reasonable. And unforgiving :)
> I think we had discussion before and some previous patches were
> bailing out to some default/basic vnuma
> configuration (when possible) in case of 'recoverable'  errors in config.
> 

Since this is new I would start with strict then consider recoverable
configs later. It's hard to code for something that's not yet well
defined.

> Any sanity checks for distances?
> 

The same applies, what is a valid distance what is not? I guess zero is
not valid? Or do we enforce that the distance to local node must be
smaller than or equal to the distance to remote node?

Wei.

> >
> > Wei.
> >
> >> Thanks,
> >> Ian.
> 
> 
> 
> -- 
> Elena

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