From mboxrd@z Thu Jan  1 00:00:00 1970
From: Ian Campbell <ian.campbell@citrix.com>
Subject: Re: [PATCH for 4.6 v3 2/3] xl/libxl: disallow saving a
 guest with vNUMA configured
Date: Fri, 11 Sep 2015 14:59:07 +0100
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To: Wei Liu <wei.liu2@citrix.com>
Cc: Xen-devel <xen-devel@lists.xenproject.org>, Ian Jackson <Ian.Jackson@eu.citrix.com>, andrew.cooper3@citrix.com
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On Fri, 2015-09-11 at 14:43 +0100, Wei Liu wrote:
> On Fri, Sep 11, 2015 at 02:21:17PM +0100, Ian Campbell wrote:
> > On Fri, 2015-09-11 at 11:50 +0100, Ian Campbell wrote:
> > > But "is d->vnuma" corresponds to there being vnuma config for the
> > > domain. 
> > 
> > We discussed this IRL and concluded that we should stop trying to
> > differentiate "no vnuma configuration" from "has empty vnuma
> > configuration".
> > 
> > So this code should raise this error if xc_domain_getvnuma returns
> > anything
> > other than rc == -1 && errno == XEN_EOPNOTSUPP. So the check is
> > 
> >     if ( rc != -1 || errno != XEN_EOPNOTSUPP )
> > 
> 
> To be precise, this should be
> 
>       if ( rc != -1 || errno == XEN_EOPNOTSUPP )
> 
> (your if expression contradicts what you said)

I don't think it did, but they are inverses of each other, due to the
"other than" wording in the prose.
		errno == OPNOTSUPP	errno != OPNOTSUPP
rc >=0		???			Some vnuma config
rc ==-1		No vnuma config(*)	Some other error

(*) is the only situation which is allowed, which is what I described in
the text.

But the if needs to reject the other 3 cases, so it is in the inverse test.
rc != -1 covers the top row, and errno != OPNOTSUPP covers the second
column, if either are true then we do not want to proceed.

Ian.