Double piwik installation and 1 login

I have installed 2 piwik (tomcat server) on 2 different machines; they have an LDAP plugin in order to log through corporate datastore.

Many users of piwik have to see the dashboard of both piwiks. How can I configure the two piwik in order to handle 1 login for users ? Each user wants to login once (for example on Piwik1) and then land on Piwik2 without reentering username and password.

Thank you in advance