From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: #599161: Xen debug patch for the "clock shifts by 50 minutes" bug. Date: Thu, 08 Nov 2012 14:34:46 +0000 Message-ID: References: <1352384924.12977.103.camel@hastur.hellion.org.uk> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1352384924.12977.103.camel@hastur.hellion.org.uk> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Ian Campbell Cc: "Philippe.Simonet@swisscom.com" , "599161@bugs.debian.org" <599161@bugs.debian.org>, "mrsanna1@gmail.com" , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 08/11/2012 14:28, "Ian Campbell" wrote: >>> There appears to be a certain amount of hardware-specificness to the >>> issue -- so I'm wondering if maybe there are some platforms whose tsc is >>> not as monotonically increasing as it needs to be... >> >> plt_* timestamps are not derived from TSC at all. > > I see, rather it is derived from the platform_timesource which could be > HPET, pmtimer, pit etc but in this case (according to the provided xm > dmesg) appears to be a 14MHz HPET. > > So I guess s/tsc/HPET/ in my original thought... In fact plt_now and plt_wrap are both derived from the same value of plt_stamp64. One is derived from it directly, and the other from plt_stamp64+plt_mask+1 (== plt_stamp64+(1<<32)). -- Keir