From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: The HPET issue on Linux Date: Wed, 6 Jan 2010 21:44:11 +0200 Message-ID: <20100106194411.GA24476@redhat.com> References: <201001061748.52689.sheng@linux.intel.com> <20100106100957.GF4905@redhat.com> <4B44648F.2010702@redhat.com> <4B44D82A.9030805@us.ibm.com> <4B44E27F.6090406@us.ibm.com> <4B44E330.4080805@codemonkey.ws> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Beth Kon , dlaor@redhat.com, Sheng Yang , kvm@vger.kernel.org To: Anthony Liguori Return-path: Received: from mx1.redhat.com ([209.132.183.28]:51127 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932647Ab0AFTo0 (ORCPT ); Wed, 6 Jan 2010 14:44:26 -0500 Content-Disposition: inline In-Reply-To: <4B44E330.4080805@codemonkey.ws> Sender: kvm-owner@vger.kernel.org List-ID: On Wed, Jan 06, 2010 at 01:23:28PM -0600, Anthony Liguori wrote: > On 01/06/2010 01:20 PM, Beth Kon wrote: > >Beth Kon wrote: > >>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? > >Anthony just explained that on x86, even edge-triggered interrupts > >are queued in the apic and an eoi will occur, so this is not > >different than the PIT. > > Not quite queued in the sense that multiple events will be delivered > in order, but I think the point is that you can still detect whether > delivery succeeded by counting APIC EOIs. > > The trouble is that historically we've struggled with doing this in > userspace. Maybe it's time to revisit. > We reinject PIT interrupts from kernel and RTC interrupts from userspace. -- Gleb.