From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([208.118.235.92]:51427) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TJKu9-0001dg-Mc for qemu-devel@nongnu.org; Wed, 03 Oct 2012 05:06:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TJKtz-0007B0-VU for qemu-devel@nongnu.org; Wed, 03 Oct 2012 05:06:09 -0400 Received: from mout.web.de ([212.227.17.11]:63409) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TJKtz-0007Av-Ll for qemu-devel@nongnu.org; Wed, 03 Oct 2012 05:05:59 -0400 Message-ID: <506BFFE6.8070701@web.de> Date: Wed, 03 Oct 2012 11:05:42 +0200 From: Jan Kiszka 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> <506BE222.6070508@msgid.tls.msk.ru> In-Reply-To: <506BE222.6070508@msgid.tls.msk.ru> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="------------enigF1FE85441D2EB3ED15986BEC" 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: Michael Tokarev Cc: kvm , Scott Moser , Marcelo Tosatti , Markus Armbruster , qemu-devel , Avi Kivity , Anthony Liguori , Cole Robinson , Paolo Bonzini , Bruce Rogers , =?UTF-8?B?QW5kcmVhcyBGw6RyYmVy?= This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF1FE85441D2EB3ED15986BEC Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 2012-10-03 08:58, Michael Tokarev wrote: > On 02.10.2012 11:46, Markus Armbruster wrote: >> "Daniel P. Berrange" writes: >=20 >>> IMHO, default to KVM, fallback to TCG is the most friendly default >>> behaviour. >> >> Friendly perhaps, generating an infinite series of questions "why is m= y >> guest slow as molasses?" certainly. >=20 > 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. >=20 > Every howto nowadays mentions kvm modules and /dev/kvm device > permissions. >=20 >> 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. >=20 > This is, again, I think, unfair. With the warning message it becomes > more or less obvious. >=20 > 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. >=20 > 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. >=20 > So the best thing to do is what Daniel, Aurelien, Paolo and others > are suggested: accel=3Dkvm:tcg with a warning. Well, we had a lot of problems with such a fallback in the past, but I think we had no proper warnings back then. I'm not fully believing in users will always realize the console message. I would therefore suggest to change the window title of QEMU as well if we fail to initialize some accelerator. Something like "QEMU without KVM" (could be "QEMU without $FAILED_ACCEL" in the end, i.e. not just for KVM). If that makes sense for everyone, I'll hack the required patches. Jan --------------enigF1FE85441D2EB3ED15986BEC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.16 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://www.enigmail.net/ iEYEARECAAYFAlBr/+YACgkQitSsb3rl5xTkugCePHuvG9FOXgLFTp7DSKqf61jI nDQAoJczenMb0ZqEhliKzreeu1EESm4U =gnAJ -----END PGP SIGNATURE----- --------------enigF1FE85441D2EB3ED15986BEC--