>>> On 23.06.16 at 11:23, <marma...@invisiblethingslab.com> wrote:
> On Thu, Jun 23, 2016 at 11:18:24AM +0200, Marek Marczykowski-Górecki wrote:
>> On Thu, Jun 23, 2016 at 03:12:47AM -0600, Jan Beulich wrote:
>> > >>> On 23.06.16 at 10:57, <marma...@invisiblethingslab.com> wrote:
>> > > On Thu, Jun 23, 2016 at 02:32:29AM -0600, Jan Beulich wrote:
>> > >> I wonder what good the duplication of the returned domain ID does: I'm
>> > >> tempted to remove the one in the command-specific structure. Does
>> > >> anyone have insight into why it was done that way?
>> > >
>> > > Isn't XEN_DOMCTL_getdomaininfo supposed to return info about first
>> > > existing domain with ID >= passed one? Reading various comments in code
>> > > it looks to be used to domain enumeration. This patch changes this
>> > > behaviour.
>> >
>> > No, it doesn't. It adjusts the behavior only for the DM case (which
>> > isn't supposed to get information on other than the target domain,
>> > i.e. in this one specific case the very domain ID needs to be passed
>> > in).
>>
>> int xc_domain_getinfo(xc_interface *xch,
>> uint32_t first_domid,
>> unsigned int max_doms,
>> xc_dominfo_t *info)
>> {
>> unsigned int nr_doms;
>> uint32_t next_domid = first_domid;
>> DECLARE_DOMCTL;
>> int rc = 0;
>>
>> memset(info, 0, max_doms*sizeof(xc_dominfo_t));
>>
>> for ( nr_doms = 0; nr_doms < max_doms; nr_doms++ )
>> {
>> domctl.cmd = XEN_DOMCTL_getdomaininfo;
>> domctl.domain = (domid_t)next_domid;
>> if ( (rc = do_domctl(xch, &domctl)) < 0 )
>> break;
>> info->domid = (uint16_t)domctl.domain;
>> (...)
>> next_domid = (uint16_t)domctl.domain + 1;
>>
>>
>> Looks like heavily dependent on XEN_DOMCTL_getdomaininfo returning next
> valid
>> domain.
>
> Hmm, looks like I've misread you patch. Reading again...
>
> But now I see rcu_read_lock(&domlist_read_lock) is gets called only when
> looping over domains, but rcu_read_unlock is called in any case. Is it
> correct?
How that? There is this third hunk:
@@ -885,6 +892,9 @@ long do_domctl(XEN_GUEST_HANDLE_PARAM(xe
copyback = 1;
getdomaininfo_out:
+ if ( dom == DOMID_INVALID )
+ break;
+
rcu_read_unlock(&domlist_read_lock);
d = NULL;
break;
Jan
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