From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH uq/master] kvm: Drop unused kvm_pit_in_kernel Date: Thu, 22 Mar 2012 14:27:37 +0100 Message-ID: <4F6B28C9.9090408@siemens.com> References: <4F69CB66.8080903@siemens.com> <4F69D946.3040800@redhat.com> <4F69DA23.8070108@siemens.com> <20120321134157.GT22368@redhat.com> <4F69DC55.3030102@siemens.com> <20120322071827.GW22368@redhat.com> <4F6B1DEE.1020502@siemens.com> <20120322125236.GG22368@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Marcelo Tosatti , kvm , qemu-devel To: Gleb Natapov Return-path: Received: from thoth.sbs.de ([192.35.17.2]:32416 "EHLO thoth.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755608Ab2CVN1y (ORCPT ); Thu, 22 Mar 2012 09:27:54 -0400 In-Reply-To: <20120322125236.GG22368@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2012-03-22 13:52, Gleb Natapov wrote: > On Thu, Mar 22, 2012 at 01:41:18PM +0100, Jan Kiszka wrote: >> On 2012-03-22 08:18, Gleb Natapov wrote: >>> On Wed, Mar 21, 2012 at 02:49:09PM +0100, Jan Kiszka wrote: >>>> On 2012-03-21 14:41, Gleb Natapov wrote: >>>>> On Wed, Mar 21, 2012 at 02:39:47PM +0100, Jan Kiszka wrote: >>>>>> On 2012-03-21 14:36, Avi Kivity wrote: >>>>>>> On 03/21/2012 02:36 PM, Jan Kiszka wrote: >>>>>>>> This is now implied by kvm_irqchip_in_kernel. >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> So we can't have -no-kvm-pit? >>>>>>> >>>>>>> No huge loss, but unexpected. >>>>>> >>>>>> See e81dda195556e72f8cd294998296c1051aab30a8. >>>>>> >>>>> I am curious what is the reason for upstream to not supporting disabling the >>>>> in-kernel PIT separately? >>>> >>>> It was considered no longer relevant: >>>> http://thread.gmane.org/gmane.comp.emulators.kvm.devel/85393 >>>> >>> Hmm, may be we should think about this some more. If in the (not so far) >>> future we want to drop pit emulation from the kernel we may want to support >>> -no-kvm-pit to allow migration from old kernels to new one. >> >> That's not an issue. Both device models are compatible, and you can >> migrate between kernel_irqchip=on/off theses days with QEMU. >> > Cool. Including PIT lost tick compensation? The feature is not yet available for the userspace PIT (we only support tick compensation for the userspace RTC - IIRC). Requires better IRQ injection feedback, you likely remember. ;) Also, I wonder if the kernel exports all tick-compensation related states for save/restore. Need to check again... Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:41206) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SAi3c-0006G1-QE for qemu-devel@nongnu.org; Thu, 22 Mar 2012 09:28:05 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1SAi3S-0000hp-Hl for qemu-devel@nongnu.org; Thu, 22 Mar 2012 09:28:00 -0400 Received: from thoth.sbs.de ([192.35.17.2]:22580) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1SAi3S-0000hH-7l for qemu-devel@nongnu.org; Thu, 22 Mar 2012 09:27:50 -0400 Message-ID: <4F6B28C9.9090408@siemens.com> Date: Thu, 22 Mar 2012 14:27:37 +0100 From: Jan Kiszka MIME-Version: 1.0 References: <4F69CB66.8080903@siemens.com> <4F69D946.3040800@redhat.com> <4F69DA23.8070108@siemens.com> <20120321134157.GT22368@redhat.com> <4F69DC55.3030102@siemens.com> <20120322071827.GW22368@redhat.com> <4F6B1DEE.1020502@siemens.com> <20120322125236.GG22368@redhat.com> In-Reply-To: <20120322125236.GG22368@redhat.com> Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH uq/master] kvm: Drop unused kvm_pit_in_kernel List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Gleb Natapov Cc: Marcelo Tosatti , Avi Kivity , kvm , qemu-devel On 2012-03-22 13:52, Gleb Natapov wrote: > On Thu, Mar 22, 2012 at 01:41:18PM +0100, Jan Kiszka wrote: >> On 2012-03-22 08:18, Gleb Natapov wrote: >>> On Wed, Mar 21, 2012 at 02:49:09PM +0100, Jan Kiszka wrote: >>>> On 2012-03-21 14:41, Gleb Natapov wrote: >>>>> On Wed, Mar 21, 2012 at 02:39:47PM +0100, Jan Kiszka wrote: >>>>>> On 2012-03-21 14:36, Avi Kivity wrote: >>>>>>> On 03/21/2012 02:36 PM, Jan Kiszka wrote: >>>>>>>> This is now implied by kvm_irqchip_in_kernel. >>>>>>>> >>>>>>>> >>>>>>> >>>>>>> So we can't have -no-kvm-pit? >>>>>>> >>>>>>> No huge loss, but unexpected. >>>>>> >>>>>> See e81dda195556e72f8cd294998296c1051aab30a8. >>>>>> >>>>> I am curious what is the reason for upstream to not supporting disabling the >>>>> in-kernel PIT separately? >>>> >>>> It was considered no longer relevant: >>>> http://thread.gmane.org/gmane.comp.emulators.kvm.devel/85393 >>>> >>> Hmm, may be we should think about this some more. If in the (not so far) >>> future we want to drop pit emulation from the kernel we may want to support >>> -no-kvm-pit to allow migration from old kernels to new one. >> >> That's not an issue. Both device models are compatible, and you can >> migrate between kernel_irqchip=on/off theses days with QEMU. >> > Cool. Including PIT lost tick compensation? The feature is not yet available for the userspace PIT (we only support tick compensation for the userspace RTC - IIRC). Requires better IRQ injection feedback, you likely remember. ;) Also, I wonder if the kernel exports all tick-compensation related states for save/restore. Need to check again... Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux