From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH 1/2] x86/VPMU: Disable VPMU when NMI watchdog is on Date: Thu, 29 Jan 2015 11:54:56 +0000 Message-ID: <54CA1F90.2040204@citrix.com> References: <1422474991-2001-1-git-send-email-boris.ostrovsky@oracle.com> <1422474991-2001-2-git-send-email-boris.ostrovsky@oracle.com> <54C95970.4050601@citrix.com> <54C963A9.8050709@oracle.com> <54C9657D.2010905@citrix.com> <54C97277.4070606@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1YGngb-0006QE-RJ for xen-devel@lists.xenproject.org; Thu, 29 Jan 2015 11:55:01 +0000 In-Reply-To: <54C97277.4070606@oracle.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Boris Ostrovsky , JBeulich@suse.com Cc: xen-devel@lists.xenproject.org, kevin.tian@intel.com, dietmar.hahn@ts.fujitsu.com List-Id: xen-devel@lists.xenproject.org On 28/01/15 23:36, Boris Ostrovsky wrote: > On 01/28/2015 05:41 PM, Andrew Cooper wrote: >> On 28/01/2015 22:33, Boris Ostrovsky wrote: >>> On 01/28/2015 04:49 PM, Andrew Cooper wrote: >>>> On 28/01/2015 19:56, Boris Ostrovsky wrote: >>>>> NMI watchdog sets APIC_LVTPC register to generate an NMI when PMU >>>>> counter >>>>> overflow occurs. This may be overwritten by VPMU code later, >>>>> effectively >>>>> turning off the watchdog. >>>>> >>>>> We should disable VPMU when NMI watchdog is running. >>>>> >>>>> Signed-off-by: Boris Ostrovsky >>>> >>>> I completely agree with the aim, but this patch is clunky and you have >>>> missed the case where neither 'watchdog' nor 'vpmu' is specified on >>>> the >>>> command line, but the booleans have been tweaked (which is the >>>> XenServer >>>> way of choosing defaults while keeping the length of the command line >>>> down). >>> >>> You mean binary patching? Or does XenServer change those flags before >>> compilation? Yes, I haven't thought about this. >> >> We patch the source before compiling. >> >> https://github.com/xenserver/xen-4.5.pg/blob/master/master/xen-tweak-cmdline-defaults.patch >> > > > How does this enable NMI watchdog? This patch sets watchdog_force but > that alone doesn't enable anything. Or are there other changes that > set opt_watchdog (which I was going to test as you suggested below). > It doesn't. I was just citing a plausible example. (For reasons which temporally elude me, "watchdog" is still a set as a proper item on the command line). Apologies if I was not clear. ~Andrew