On Thu, 19 Oct 2023, Jan Beulich wrote: > On 18.10.2023 23:31, Stefano Stabellini wrote: > > On Wed, 17 Oct 2023, Jan Beulich wrote: > >> > >> On 14.10.2023 01:06, Stefano Stabellini wrote: > >>> From: George Dunlap <[email protected]> > >>> > >>> Commit fc2b57c9a ("xenstored: send an evtchn notification on > >>> introduce_domain") introduced the sending of an event channel to the > >>> guest when first introduced, so that dom0less domains waiting for the > >>> connection would know that xenstore was ready to use. > >>> > >>> Unfortunately, it was introduced in introduce_domain(), which 1) is > >>> called by other functions, where such functionality is unneeded, and > >>> 2) after the main XS_INTRODUCE call, calls domain_conn_reset(). This > >>> introduces a race condition, whereby if xenstored is delayed, a domain > >>> can wake up, send messages to the buffer, only to have them deleted by > >>> xenstore before finishing its processing of the XS_INTRODUCE message. > >>> > >>> Move the connect-and-notfy call into do_introduce() instead, after the > >>> domain_conn_rest(); predicated on the state being in the > >>> XENSTORE_RECONNECT state. > >>> > >>> (We don't need to check for "restoring", since that value is always > >>> passed as "false" from do_domain_introduce()). > >>> > >>> Also take the opportunity to add a missing wmb barrier after resetting > >>> the indexes of the ring in domain_conn_reset. > >>> > >>> This change will also remove an extra event channel notification for > >>> dom0 (because the notification is now done by do_introduce which is not > >>> called for dom0.) The extra dom0 event channel notification was only > >>> introduced by fc2b57c9a and was never present before. It is not needed > >>> because dom0 is the one to tell xenstored the connection parameters, so > >>> dom0 has to know that the ring page is setup correctly by the time > >>> xenstored starts looking at it. It is dom0 that performs the ring page > >>> init. > >>> > >>> Signed-off-by: George Dunlap <[email protected]> > >>> Signed-off-by: Stefano Stabellini <[email protected]> > >> > >> Should this have had a Fixes: tag thus marking it to pick up for > >> backport? > > > > Sorry this was committed already > > That's why I used "have had". I still need an answer to the question > though; your reply only hints towards "yes".
Yes, I would add the Fixes tag
