On 29/04/2020 14:22, Paul Durrant wrote: >> -----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.
To clarify, what I meant is that once crash happened (before kdump kernel is loaded) toolstack gets code 5 and then it's supposed to call soft reset and unpause the domain to actually load into crash kernel. I didn't mean that after crash kernel is finished the domain has to be restarted - that's obvious. Igor
