From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: AMD Magny-Cours and HPET Date: Tue, 16 Aug 2011 10:47:13 +0100 Message-ID: <4E4A3CA1.3050100@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Return-path: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: "xen-devel@lists.xensource.com" , Christoph Egger , Wei Huang List-Id: xen-devel@lists.xenproject.org Hello, We have had a bug raised against Xen-3.4 that the kexec path fails, on HP BL465c G7 blades. The problem does not reproduce on any other AMD machines I have to hand. On further investigation, it appears that if the crashing cpu is #0, then the kexec path hangs forever trying to grab the already locked legacy_hpet_event.lock in hpet_disable_legacy_broadcast(). Removing the lock/unlock pair causes the kexec crash path to work as expected. If the crashing cpu is not #0, then local_time_calibration() gets worried and dumps the calibration data, and hangs at some later point which I have yet to find. This hang happens while performing the NMI shootdown of other cpus. The support engineer who raised the bug says that it doesn't occur with Xen-4.1. Is there anything architecturally new in the Magny-Cours processors which might explain this behavior? I am unwilling to try and backport the hpet code from Xen-4.x without understanding the problem, although it is a possible solution. Thanks -- Andrew Cooper - Dom0 Kernel Engineer, Citrix XenServer T: +44 (0)1223 225 900, http://www.citrix.com