Re: [Xen-devel] [PATCH v5 5/7] libxl: allow creation of domains with a specified or random domid

["Durrant, Paul" <pdurrant@xxxxxxxxxxxx>]

> -----Original Message-----
> From: jandryuk@xxxxxxxxx <jandryuk@xxxxxxxxx>
> Sent: 31 January 2020 17:23
> To: Durrant, Paul <pdurrant@xxxxxxxxxxxx>
> Cc: xen-devel <xen-devel@xxxxxxxxxxxxxxxxxxxx>; Ian Jackson
> <ian.jackson@xxxxxxxxxxxxx>; Wei Liu <wl@xxxxxxx>; Anthony PERARD
> <anthony.perard@xxxxxxxxxx>; Andrew Cooper <andrew.cooper3@xxxxxxxxxx>;
> George Dunlap <George.Dunlap@xxxxxxxxxxxxx>; Jan Beulich
> <jbeulich@xxxxxxxx>; Julien Grall <julien@xxxxxxx>; Konrad Rzeszutek Wilk
> <konrad.wilk@xxxxxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Subject: Re: [PATCH v5 5/7] libxl: allow creation of domains with a
> specified or random domid
> 
> On Fri, Jan 31, 2020 at 10:02 AM Paul Durrant <pdurrant@xxxxxxxxxx> wrote:
> >
> > This patch adds a 'domid' field to libxl_domain_create_info and then
> > modifies libxl__domain_make() to have Xen use that value if it is valid.
> > If the domid value is invalid then Xen will choose the domid, as before,
> > unless the value is the new special RANDOM_DOMID value added to the API.
> > This value instructs libxl__domain_make() to choose a random domid value
> > for Xen to use.
> >
> > If Xen determines that a domid specified to or chosen by
> > libxl__domain_make() co-incides with an existing domain then the create
> > operation will fail. In this case, if RANDOM_DOMID was specified to
> > libxl__domain_make() then a new random value will be chosen and the
> create
> > operation will be re-tried, otherwise libxl__domain_make() will fail.
> >
> > After Xen has successfully created a new domain, libxl__domain_make()
> will
> > check whether its domid matches any recently used domid values. If it
> does
> > then the domain will be destroyed. If the domid used in creation was
> > specified to libxl__domain_make() then it will fail at this point,
> > otherwise the create operation will be re-tried with either a new random
> > or Xen-selected domid value.
> >
> > NOTE: libxl__logv() is also modified to only log valid domid values in
> >       messages rather than any domid, valid or otherwise, that is not
> >       INVALID_DOMID.
> >
> > Signed-off-by: Paul Durrant <pdurrant@xxxxxxxxxx>
> 
> Looks good, with one suggestion below.
> 
> Reviewed-by: Jason Andryuk <jandryuk@xxxxxxxxx>
> 

Thanks.

> <snip>
> 
> > +
> > +            /* Try to destroy the domain again as we can't use it */
> > +            ret = xc_domain_destroy(ctx->xch, *domid);
> > +            if (ret < 0) {
> > +                LOGED(ERROR, *domid, "domain destroy fail");
> 
> Maybe "destroy recently used domain id failed"?
> 

Probably doesn't actually matter. A destroy failure during domain creation 
would be an unusual circumstance, but if I have to post a v6 I'll change the 
message while I'm at it.

  Paul

> > +                *domid = INVALID_DOMID;
> > +                rc = ERROR_FAIL;
> > +                goto out;
> > +            }
> >          }
> >
> >          rc = libxl__arch_domain_save_config(gc, d_config, state,
> &create);
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