> -----Original Message----- > From: Igor Druzhinin <igor.druzhi...@citrix.com> > Sent: 29 April 2020 14:17 > To: p...@xen.org; 'Jürgen Groß' <jgr...@suse.com>; 'Julien Grall' > <jul...@xen.org>; 'Julien Grall' > <julien.grall....@gmail.com> > Cc: 'xen-devel' <xen-devel@lists.xenproject.org>; 'Ian Jackson' > <ian.jack...@eu.citrix.com>; 'Wei Liu' > <w...@xen.org>; andrew.coop...@citrix.com > Subject: Re: [PATCH] tools/xenstore: don't store domU's mfn of ring page in > xensotred > > On 29/04/2020 13:56, Paul Durrant wrote: > >> -----Original Message----- > >> From: Igor Druzhinin <igor.druzhi...@citrix.com> > >> Sent: 29 April 2020 13:50 > >> To: Jürgen Groß <jgr...@suse.com>; Julien Grall <jul...@xen.org>; Julien > >> Grall > >> <julien.grall....@gmail.com> > >> Cc: xen-devel <xen-devel@lists.xenproject.org>; Ian Jackson > >> <ian.jack...@eu.citrix.com>; Wei Liu > >> <w...@xen.org>; andrew.coop...@citrix.com; Paul Durrant <p...@xen.org> > >> Subject: Re: [PATCH] tools/xenstore: don't store domU's mfn of ring page > >> in xensotred > >> > >> On 29/04/2020 13:29, Jürgen Groß wrote: > >>> > >>> Wei, Ian, can you please tell me where I'm wrong? > >>> > >>> A soft reset should restart the domain in a clean state. AFAIK libxl is > >>> handling that by doing kind of in-place save-restore, including calling > >>> xs_release_domain() and later xs_introduce_domain(). This should result > >>> in xenstored throwing away all state it has regarding the domain and > >>> then restarting with a new (internal) domain instance. > >>> > >>> Is XAPI doing soft reset differently? Why should there be a need for > >>> keeping xenstored data across a soft reset? > >> > >> Yes, XAPI is doing soft reset differently from libxl. You need to keep > >> xenstore > >> data to at least keep backends working without the need to reinitialize > >> them > >> before entering kdump kernel. We do the same thing while entering crash > >> kernel > >> in Windows after BSOD (CC Paul as he recommended this approach). > > > > IIRC I recommended not involving Xen or the toolstack in entering the crash > > kernel... they don't > need to know. Windows quite happily enters its crash kernel, rebuilds its Xen > interfaces and re- > attaches to PV backends without any external intervention. > > In case of kdump toolstack certainly needs to know as it gets shutdown code 5 > and > needs to restart the domain. >
The toolstack needs to restart the domain once the crash has completed, yes. > And I'm not completely sure it's possible to enter kdump without calling soft > reset > at all. Even if it's possible I'd be cautious to do it in production for the > future. > If it is not possible at the moment then IMO it should be made so; having soft reset in the toolstack is a layering violation IMO. Paul
