From mboxrd@z Thu Jan 1 00:00:00 1970 From: Michael Tokarev Subject: Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if the host supports it Date: Wed, 03 Oct 2012 10:58:42 +0400 Message-ID: <506BE222.6070508@msgid.tls.msk.ru> References: <20120930191146.GA20012@amt.cnet> <50694EC1.8060006@siemens.com> <20121001093102.GA14797@amt.cnet> <50696E9E.7030302@siemens.com> <87zk468h3y.fsf@codemonkey.ws> <50699CDC.1010604@redhat.com> <87wqzap9ui.fsf@codemonkey.ws> <5069A9DF.4040606@siemens.com> <5069C814.7010201@suse.de> <20121001164730.GC15554@redhat.com> <87zk4571vf.fsf@blackfin.pond.sub.org> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: "Daniel P. Berrange" , kvm , Scott Moser , Jan Kiszka , Marcelo Tosatti , qemu-devel , Bruce Rogers , Avi Kivity , Anthony Liguori , Cole Robinson , Paolo Bonzini , =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= To: Markus Armbruster Return-path: Received: from isrv.corpit.ru ([86.62.121.231]:39593 "EHLO isrv.corpit.ru" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752570Ab2JCG6q (ORCPT ); Wed, 3 Oct 2012 02:58:46 -0400 In-Reply-To: <87zk4571vf.fsf@blackfin.pond.sub.org> Sender: kvm-owner@vger.kernel.org List-ID: On 02.10.2012 11:46, Markus Armbruster wrote: > "Daniel P. Berrange" writes: >> IMHO, default to KVM, fallback to TCG is the most friendly default >> behaviour. > > Friendly perhaps, generating an infinite series of questions "why is my > guest slow as molasses?" certainly. With a warning about "switching to slow emulation mode because .." printed at startup that becomes a non-issue, because there's no reason to ask more questions about why it is slow - it already said why. Yes some may try to ask what to do, which is different. Every howto nowadays mentions kvm modules and /dev/kvm device permissions. > And for each instance of the question, there's an unknown number of > users who give QEMU a quick try, screw up KVM unknowingly, observe the > glacial speed, and conclude it's crap. This is, again, I think, unfair. With the warning message it becomes more or less obvious. If you're talking about users who run it with -daemonize argument - this is a) stupid to do when TRYING it out, so it's not a big deal to lose another stupid user, and b) qemu should init everything first and throw all warnings and fatal errors before daemonizing, if this is not the case it should be fixed in the code. And if you're talking about management software (libvirt and others), it controls all the required privileges already and explicitly requests acceleration and other stuff. So the best thing to do is what Daniel, Aurelien, Paolo and others are suggested: accel=kvm:tcg with a warning. Thanks, /mjt From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:34326) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TJIv0-0006sj-LF for qemu-devel@nongnu.org; Wed, 03 Oct 2012 02:58:58 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TJIuz-0004we-K4 for qemu-devel@nongnu.org; Wed, 03 Oct 2012 02:58:54 -0400 Received: from isrv.corpit.ru ([86.62.121.231]:48810) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TJIuz-0004v7-Cb for qemu-devel@nongnu.org; Wed, 03 Oct 2012 02:58:53 -0400 Message-ID: <506BE222.6070508@msgid.tls.msk.ru> Date: Wed, 03 Oct 2012 10:58:42 +0400 From: Michael Tokarev MIME-Version: 1.0 References: <20120930191146.GA20012@amt.cnet> <50694EC1.8060006@siemens.com> <20121001093102.GA14797@amt.cnet> <50696E9E.7030302@siemens.com> <87zk468h3y.fsf@codemonkey.ws> <50699CDC.1010604@redhat.com> <87wqzap9ui.fsf@codemonkey.ws> <5069A9DF.4040606@siemens.com> <5069C814.7010201@suse.de> <20121001164730.GC15554@redhat.com> <87zk4571vf.fsf@blackfin.pond.sub.org> In-Reply-To: <87zk4571vf.fsf@blackfin.pond.sub.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] kvm: Set default accelerator to "kvm" if the host supports it List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster Cc: kvm , Scott Moser , Jan Kiszka , Marcelo Tosatti , qemu-devel , Bruce Rogers , Avi Kivity , Anthony Liguori , Cole Robinson , Paolo Bonzini , =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= On 02.10.2012 11:46, Markus Armbruster wrote: > "Daniel P. Berrange" writes: >> IMHO, default to KVM, fallback to TCG is the most friendly default >> behaviour. > > Friendly perhaps, generating an infinite series of questions "why is my > guest slow as molasses?" certainly. With a warning about "switching to slow emulation mode because .." printed at startup that becomes a non-issue, because there's no reason to ask more questions about why it is slow - it already said why. Yes some may try to ask what to do, which is different. Every howto nowadays mentions kvm modules and /dev/kvm device permissions. > And for each instance of the question, there's an unknown number of > users who give QEMU a quick try, screw up KVM unknowingly, observe the > glacial speed, and conclude it's crap. This is, again, I think, unfair. With the warning message it becomes more or less obvious. If you're talking about users who run it with -daemonize argument - this is a) stupid to do when TRYING it out, so it's not a big deal to lose another stupid user, and b) qemu should init everything first and throw all warnings and fatal errors before daemonizing, if this is not the case it should be fixed in the code. And if you're talking about management software (libvirt and others), it controls all the required privileges already and explicitly requests acceleration and other stuff. So the best thing to do is what Daniel, Aurelien, Paolo and others are suggested: accel=kvm:tcg with a warning. Thanks, /mjt