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? Jan
