From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: KEXEC: allocate crash note buffers at boot time v5 Date: Fri, 2 Dec 2011 16:27:54 +0000 Message-ID: <4ED8FC8A.7040002@citrix.com> References: <4ED906BA020000780006523E@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <4ED906BA020000780006523E@nat28.tlf.novell.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: Jan Beulich Cc: Keir Fraser , "xen-devel@lists.xensource.com" List-Id: xen-devel@lists.xenproject.org On 02/12/11 16:11, Jan Beulich wrote: >>>> On 02.12.11 at 16:59, Andrew Cooper wrote: >> On 02/12/11 15:43, Jan Beulich wrote: >>> I just had another look at the Dom0 side of things, and I fail to see why >>> you think boot time allocation is necessary: All Dom0 does with the >>> provided info is set up the resource tree. The data doesn't get stored >>> for any post-boot use. What am I overlooking? >> /sbin/kexec opens /proc/iomem and looks for "Crash note" and interprets >> the range values. This is how it grabs the locations to pack into its >> magic binary package. > So how does the hotplug scenario then get handled on native? I can't > imagine they expect things to remain stable across CPU unplug and > re-activation. > > Jan I am not how (or even if) the hotplug condition is handled on native. I guess it depends on what is put into the resource tree on boot. With my patch, Xen will give crash areas for all pcpus up to nr_cpu_ids, which covers all the cases. The worst that will happen is that some crash notes do not get written if certain cpus are offline at the time of a crash. -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com