From mboxrd@z Thu Jan 1 00:00:00 1970 From: Olaf Hering Subject: Re: [PATCH] xenstored: allow guests to reintroduce themselves Date: Tue, 9 Aug 2011 11:17:14 +0200 Message-ID: <20110809091714.GA6436@aepfle.de> References: <1312880369.26263.33.camel@zakaz.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Return-path: Content-Disposition: inline In-Reply-To: <1312880369.26263.33.camel@zakaz.uk.xensource.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: Ian Campbell Cc: "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On Tue, Aug 09, Ian Campbell wrote: > On Mon, 2011-08-01 at 13:38 +0100, Olaf Hering wrote: > > # HG changeset patch > > # User Olaf Hering > > # Date 1312202176 -7200 > > # Node ID edb96c34f4a638e8ba97933b6bd76ff72836353e > > # Parent 0f36c2eec2e1576b4db6538b5f22d625587c1a15 > > xenstored: allow guests to reintroduce themselves > > > > During kexec all old watches have to be removed, otherwise the new > > kernel will receive unexpected events. Allow a guest to introduce itself > > and cleanup all of its watches. > > Just out of interest what happens if a guest tries to use this operation > on an older xenstored which does not support it? I guess it gets an > enosys type response? It does, conn->id is not zero and the modified function returns early. > Is there any way we can arrange to probe for this feature in order to > fail to register for kexec/kdump early on rather than failing at the > point where we attempt to actually kexec (where failure might come as > rather an unpleasant surprise). I don't think we've historically had a > mechanism for negotiating features with xenstored itself so I'm not sure > what would be best here. Perhaps xenstored itself should > expose /xenstored/feature-FOO nodes? This patch is only for kexec boots, with kdump the crash in the kdump kernel may happen as well but so far I have not seen it. Maybe because the kdump kernel runs in its own memory range. If you prefer, kexec can be modified to check for certain xenstored properties. Olaf