From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sheng Yang Subject: The HPET issue on Linux Date: Wed, 6 Jan 2010 17:48:52 +0800 Message-ID: <201001061748.52689.sheng@linux.intel.com> Mime-Version: 1.0 Content-Type: Text/Plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Cc: kvm@vger.kernel.org To: Beth Kon Return-path: Received: from mga09.intel.com ([134.134.136.24]:13551 "EHLO mga09.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755337Ab0AFJup (ORCPT ); Wed, 6 Jan 2010 04:50:45 -0500 Sender: kvm-owner@vger.kernel.org List-ID: 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. -- regards Yang, Sheng