From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: [Qemu-devel] TSC in qem[-kvm] 1.1+ and in-kernel irqchip Date: Fri, 10 Aug 2012 13:24:06 +0400 Message-ID: <5024D336.5090108@msgid.tls.msk.ru> References: <5024011F.2020200@msgid.tls.msk.ru> <20120810073346.GD24410@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: KVM list , qemu-devel , Avi Kivity , Gerd Hoffmann To: Gleb Natapov Return-path: Received: from isrv.corpit.ru ([86.62.121.231]:46590 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758131Ab2HJJYI (ORCPT ); Fri, 10 Aug 2012 05:24:08 -0400 In-Reply-To: <20120810073346.GD24410@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 10.08.2012 11:33, Gleb Natapov wrote: > On Thu, Aug 09, 2012 at 10:27:43PM +0400, Michael Tokarev wrote: >> As a follow-up to the patch "tsc: use kvmclock for >> calibration". >> >> There's another problem reported by several users. >> The sympthom is that grub does not show boot menu, >> it boots default entry right away without any pause. >> >> After quite some debugging it turned out to be >> TSC issue. Grub uses tsc for its timeout handling. >> When setting timeout to some very large value >> (10000), I can see the counter is ticking backwards >> at a very high speed, ticking from 10000 to 0 in >> about 5 seconds. >> >> Running kvm -cpu host,-tsc forces grub to use >> rtc clocksource, and the problem goes away. >> > Can you try -no-kvm-pit-reinjection please. It does not help. With -no-kvm-pit-reinjection, the time in grub is ticking about 1000 times faster still, just like without. >> The most interesting thing is that this is a >> problem new for qemu-kvm 1.1 (and is still >> present in current git), 1.0 version had no >> such issue. And it only happens when in-kernel >> irqchip is enabled -- running with -no-kvm-irqchip >> also fixes the grub problem, so that tsc starts >> counting "correctly" for grub again. >> > 1.0 work on the same kernel 1.1 doesn't? Yes. This issue does not look like kernel-dependent - it happens the same way on 3.0, 3.2 and 3.5 kernels. Note that upstream qemu 1.1+ is also affected, when used with -machine pc,kernel_irqchip=on. /mjt From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:40007) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SzlRz-00016v-74 for qemu-devel@nongnu.org; Fri, 10 Aug 2012 05:24:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SzlRx-0006d4-6y for qemu-devel@nongnu.org; Fri, 10 Aug 2012 05:24:11 -0400 Received: from isrv.corpit.ru ([86.62.121.231]:57079) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SzlRw-0006cb-P4 for qemu-devel@nongnu.org; Fri, 10 Aug 2012 05:24:09 -0400 Message-ID: <5024D336.5090108@msgid.tls.msk.ru> Date: Fri, 10 Aug 2012 13:24:06 +0400 From: Michael Tokarev MIME-Version: 1.0 References: <5024011F.2020200@msgid.tls.msk.ru> <20120810073346.GD24410@redhat.com> In-Reply-To: <20120810073346.GD24410@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] TSC in qem[-kvm] 1.1+ and in-kernel irqchip List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: Gerd Hoffmann , qemu-devel , KVM list , Avi Kivity On 10.08.2012 11:33, Gleb Natapov wrote: > On Thu, Aug 09, 2012 at 10:27:43PM +0400, Michael Tokarev wrote: >> As a follow-up to the patch "tsc: use kvmclock for >> calibration". >> >> There's another problem reported by several users. >> The sympthom is that grub does not show boot menu, >> it boots default entry right away without any pause. >> >> After quite some debugging it turned out to be >> TSC issue. Grub uses tsc for its timeout handling. >> When setting timeout to some very large value >> (10000), I can see the counter is ticking backwards >> at a very high speed, ticking from 10000 to 0 in >> about 5 seconds. >> >> Running kvm -cpu host,-tsc forces grub to use >> rtc clocksource, and the problem goes away. >> > Can you try -no-kvm-pit-reinjection please. It does not help. With -no-kvm-pit-reinjection, the time in grub is ticking about 1000 times faster still, just like without. >> The most interesting thing is that this is a >> problem new for qemu-kvm 1.1 (and is still >> present in current git), 1.0 version had no >> such issue. And it only happens when in-kernel >> irqchip is enabled -- running with -no-kvm-irqchip >> also fixes the grub problem, so that tsc starts >> counting "correctly" for grub again. >> > 1.0 work on the same kernel 1.1 doesn't? Yes. This issue does not look like kernel-dependent - it happens the same way on 3.0, 3.2 and 3.5 kernels. Note that upstream qemu 1.1+ is also affected, when used with -machine pc,kernel_irqchip=on. /mjt