Re: [Xen-devel] [PATCH 7/7] tools/libxl: Allow dom0 to be destroyed

[Daniel De Graaf <dgdegra@xxxxxxxxxxxxx>]

On 03/19/2014 07:02 AM, Ian Campbell wrote:
> On Tue, 2014-03-18 at 17:34 -0400, Daniel De Graaf wrote:
> > @@ -3076,12 +3076,13 @@ static void unpause_domain(uint32_t domid)
> >       libxl_domain_unpause(ctx, domid);
> >   }
> >
> > -static void destroy_domain(uint32_t domid)
> > +static void destroy_domain(uint32_t domid, int force)
> >   {
> >       int rc;
> >
> > -    if (domid == 0) {
> > -        fprintf(stderr, "Cannot destroy privileged domain 0.\n\n");
> > +    if (domid == 0 && !force) {
> > +        fprintf(stderr, "Destroying domain 0 is only supported in a"
> > +                " disaggregated environment and requires the -f flag.\n\n");
> > From a user point of view perhaps this would be clearer if worded
> something like:
>
>          Not destroying domain 0, use -f to force.
OK, I like that error message better.

> Is the error message on attempted self destruction informative? If not
> then append "This can only be done from another domain, e.g. a
> disaggregated toolstack domain".
libxl: error: libxl.c:1411:libxl__destroy_domid: xc_domain_pause failed for 0
libxl: error: libxl.c:1471:devices_destroy_cb: xc_domain_destroy failed for 0
libxl: error: libxl.c:1342:domain_destroy_callback: unable to destroy guest 
with domid 0
libxl: error: libxl.c:1269:domain_destroy_cb: destruction of domain 0 failed
destroy failed (rc=-3)

It seems that libxl should include the errno from the hypervisor (EINVAL
in this case) somewhere in its output.

> Last random thought: Does this code know or have the potential to know
> which domain it is running in?
Not easily; I discussed this with Ian Jackson for the v1 patch, and we
decided that determining your own domain ID here was too cumbersome.

> All of this info should also be added to the man page and the help text
> in xl_cmdtable.c needs to have the -f added to it.
Ah, yes, documentation... will do.

> >           exit(-1);
> >       }
> >       rc = libxl_domain_destroy(ctx, domid, 0);
> > @@ -4166,12 +4167,15 @@ int main_unpause(int argc, char **argv)
> >   int main_destroy(int argc, char **argv)
> >   {
> >       int opt;
> > +    int force = 0;
> >
> > -    SWITCH_FOREACH_OPT(opt, "", NULL, "destroy", 1) {
> > -        /* No options */
> > +    SWITCH_FOREACH_OPT(opt, "f", NULL, "destroy", 1) {
> > +    case 'f':
> > +        force = 1;
> > +        break;
> >       }
> >
> > -    destroy_domain(find_domain(argv[optind]));
> > +    destroy_domain(find_domain(argv[optind]), force);
> >       return 0;
> >   }

--
Daniel De Graaf
National Security Agency

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