From mboxrd@z Thu Jan 1 00:00:00 1970 From: Beth Kon Subject: Re: The HPET issue on Linux Date: Wed, 06 Jan 2010 13:36:26 -0500 Message-ID: <4B44D82A.9030805@us.ibm.com> References: <201001061748.52689.sheng@linux.intel.com> <20100106100957.GF4905@redhat.com> <4B44648F.2010702@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Cc: Gleb Natapov , Sheng Yang , kvm@vger.kernel.org To: dlaor@redhat.com Return-path: Received: from e34.co.us.ibm.com ([32.97.110.152]:50133 "EHLO e34.co.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756001Ab0AFSgl (ORCPT ); Wed, 6 Jan 2010 13:36:41 -0500 Received: from d03relay01.boulder.ibm.com (d03relay01.boulder.ibm.com [9.17.195.226]) by e34.co.us.ibm.com (8.14.3/8.13.1) with ESMTP id o06IUoiH008265 for ; Wed, 6 Jan 2010 11:30:50 -0700 Received: from d03av06.boulder.ibm.com (d03av06.boulder.ibm.com [9.17.195.245]) by d03relay01.boulder.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id o06IaIeX154178 for ; Wed, 6 Jan 2010 11:36:18 -0700 Received: from d03av06.boulder.ibm.com (loopback [127.0.0.1]) by d03av06.boulder.ibm.com (8.14.3/8.13.1/NCO v10.0 AVout) with ESMTP id o06IcILG023190 for ; Wed, 6 Jan 2010 11:38:18 -0700 In-Reply-To: <4B44648F.2010702@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: Dor Laor wrote: > On 01/06/2010 12:09 PM, Gleb Natapov wrote: >> On Wed, Jan 06, 2010 at 05:48:52PM +0800, Sheng Yang wrote: >>> Hi Beth >>> >>> I still found the emulated HPET would result in some boot failure. For >>> example, on my 2.6.30, with HPET enabled, the kernel would fail >>> check_timer(), >>> especially in timer_irq_works(). >>> >>> The testing of timer_irq_works() is let 10 ticks pass(using >>> mdelay()), and >>> want to confirm the clock source with at least 5 ticks advanced in >>> jiffies. >>> I've checked that, on my machine, it would mostly get only 4 ticks >>> when HPET >>> enabled, then fail the test. On the other hand, if I using PIT, it >>> would get >>> more than 10 ticks(maybe understandable if some complementary ticks >>> there). Of >>> course, extend the ticks count/mdelay() time can work. >>> >>> I think it's a major issue of HPET. And it maybe just due to a too long >>> userspace path for interrupt injection... If it's true, I think it's >>> not easy >>> to deal with it. >>> >> PIT tick are reinjected automatically, HPET should probably do the same >> although it may just create another set of problems. > > Older Linux do automatic adjustment for lost ticks so automatic > reinjection causes time to run too fast. This is why we added the > -no-kvm-pit-reinject flag... > > It took lots of time to pit/rtc to stabilize, in order of seriously > consider the hpet emulation, lots of testing should be done. I will try to look into this. Since HPET is edge-triggered, looks like this problem is of a different nature than PIT. Is this a solid failure or intermittent? > >> >> -- >> Gleb. >> -- >> To unsubscribe from this list: send the line "unsubscribe kvm" in >> the body of a message to majordomo@vger.kernel.org >> More majordomo info at http://vger.kernel.org/majordomo-info.html > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Regards, Beth Kon