From mboxrd@z Thu Jan 1 00:00:00 1970 From: Gleb Natapov Subject: Re: KVM git hangs with if=virtio (works under kvm 0.12.3) Date: Mon, 5 Jul 2010 15:17:59 +0300 Message-ID: <20100705121759.GP4689@redhat.com> References: <1278041518.10459.48.camel@geektop> Mime-Version: 1.0 Content-Type: text/plain; charset=koi8-r Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: ewheeler , kvm@vger.kernel.org To: Stefan Hajnoczi Return-path: Received: from mx1.redhat.com ([209.132.183.28]:65504 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753527Ab0GEMSC convert rfc822-to-8bit (ORCPT ); Mon, 5 Jul 2010 08:18:02 -0400 Content-Disposition: inline In-Reply-To: Sender: kvm-owner@vger.kernel.org List-ID: On Mon, Jul 05, 2010 at 01:11:25PM +0100, Stefan Hajnoczi wrote: > On Fri, Jul 2, 2010 at 9:07 AM, Stefan Hajnoczi = wrote: > > On Fri, Jul 2, 2010 at 4:31 AM, ewheeler wrot= e: > >> Hello all, > >> > >> I'm booting a CentOS kernel under today's KVM git and it hangs aft= er > >> initializing the serial port when the drive if=3Dvirtio, but not w= hen > >> drive if=3Dide. =9ALook close---this is not a "forgot to add virti= o_blk" > >> problem. =9AIf I use 0.12.3 from Ubuntu 10.04 it works properly. > >> > >> Reproduction: > >> > >> Using kvm 0.12.3 on ubuntu 10.04 (1:84+dfsg-0ubuntu16+0.12.3+norom= s > >> +0ubuntu9) it will work properly: > >> > >> =9Aqemu-system-x86_64 -drive file=3Ddummy-disk-image,if=3Dvirtio \ > >> =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A =9A-kernel vmlinuz-2.6= =2E18-194.3.1.el5.centos.plus > >> > >> As expected, the kernel panics unable to mount root (good-boot.png= ). > >> This makes sense, as "dummy-disk-image" is 1MB of 0x00 bytes. > >> > >> ---However---if I use today's git (2010-07-01) of kvm: > >> > >> =9A /usr/local/kvm-git/bin/qemu-system-x86_64 -drive file=3Ddummy-= disk-image,if=3Dvirtio \ > >> =9A =9A =9A =9A-kernel vmlinuz-2.6.18-194.3.1.el5.centos.plus > >> > >> This hangs just after initializing the Serial device (obtained by = adding > >> -serial stdio -append console=3DttyS0): > >> > >> Note that this only happens with the disk interface set to virtio > >> (if=3Dvirtio). =9AIt works fine for ide (if=3Dide). > >> > >> > >> Am I doing something wrong here? > >> Is anyone else having this problem? > > > > I have seen this issue with a RHEL 5.5 guest running under > > qemu-kvm.git. =9AIt boots a new guest fine but hangs as you describ= ed > > with the RHEL 5.5 kernel. =9AI have not investigated. >=20 > This issue is affected by extboot, a feature that enables booting fro= m > virtio-blk devices. I have just sent a patch to the KVM mailing list > to restore extboot functionality which has been broken in > qemu-kvm.git. That patch can be used to work around this issue by > using "-drive ...,boot=3Don" but it doesn't explain why the RHEL 5.5 > kernel hangs during serial initialization when extboot is not present= =2E >=20 Hang that happens during guest boot (after bootloader started the kernel) cannot be worked around by extboot. extboot is also not needed with latest qemu git to boot from virtio disks since the support for that is in the bios now. =20 -- Gleb.