From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Kiszka Subject: Re: [PATCH 04/19] qemu-kvm: x86: Drop MSR reset Date: Thu, 05 May 2011 14:42:54 +0200 Message-ID: <4DC29B4E.2070500@siemens.com> References: <4DC25AF3.6050704@redhat.com> <4DC25BC5.9090801@siemens.com> <4DC25CDB.9060805@redhat.com> <4DC25F82.2040501@siemens.com> <4DC260DD.5010807@redhat.com> <4DC26388.4090207@siemens.com> <4DC265A5.90301@redhat.com> <4DC26EAA.7080803@siemens.com> <20110505112257.GE19019@redhat.com> <4DC290E3.7000507@redhat.com> <20110505122356.GA29181@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Cc: Avi Kivity , Marcelo Tosatti , "kvm@vger.kernel.org" To: Gleb Natapov Return-path: Received: from thoth.sbs.de ([192.35.17.2]:21624 "EHLO thoth.sbs.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753986Ab1EEMnB (ORCPT ); Thu, 5 May 2011 08:43:01 -0400 In-Reply-To: <20110505122356.GA29181@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: On 2011-05-05 14:23, Gleb Natapov wrote: > On Thu, May 05, 2011 at 02:58:27PM +0300, Avi Kivity wrote: >> On 05/05/2011 02:22 PM, Gleb Natapov wrote: >>>> >>>> We'll see, but I still do not share your concern regarding future >>>> regressions when removing the fragile reset code. >>>> >>> Why do we rely on userspace to properly reset kernel component anyway? >>> We should introduce cpu/lapic/ioapic/pit/pic resets ASAP. >> >> We should, but we'll always have to deal with kernels that don't >> have reset ioctls. >> > s/always/for quite a while/. Unfortunately yes. Unless we put qemu in the kernel > tree and will release them in lock steps of course :) Seriously, I do not see much added-value of a reset service. The pattern we will use for MSRs could just be applied to other in-kernel resources as well - unless they are already architecturally defined in a way that leaves no questions regarding the proper future reset state. Except for the CPU, all other in-kernel devices are not extensible in their current form. Jan -- Siemens AG, Corporate Technology, CT T DE IT 1 Corporate Competence Center Embedded Linux