From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932310Ab1KHRXB (ORCPT ); Tue, 8 Nov 2011 12:23:01 -0500 Received: from cantor2.suse.de ([195.135.220.15]:45456 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754448Ab1KHRW6 (ORCPT ); Tue, 8 Nov 2011 12:22:58 -0500 Message-ID: <4EB96829.1010709@suse.de> Date: Tue, 08 Nov 2011 18:34:33 +0100 From: Alexander Graf User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.14) Gecko/20110221 SUSE/3.1.8 Thunderbird/3.1.8 MIME-Version: 1.0 To: Christoph Hellwig Cc: Avi Kivity , Linus Torvalds , Ingo Molnar , "linux-kernel@vger.kernel.org List" , "kvm@vger.kernel.org list" , qemu-devel Developers , Pekka Enberg , Am?rico Wang , Blue Swirl Subject: Re: [PATCH] KVM: Add wrapper script around QEMU to test kernels References: <1320543320-32728-1-git-send-email-agraf@suse.de> <4EB93FA4.8020800@redhat.com> <20111108145257.GA10846@infradead.org> <4EB94340.5040205@redhat.com> <20111108145945.GA17842@infradead.org> In-Reply-To: <20111108145945.GA17842@infradead.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 11/08/2011 03:59 PM, Christoph Hellwig wrote: > On Tue, Nov 08, 2011 at 04:57:04PM +0200, Avi Kivity wrote: >>> Running qemu -snapshot on the actual root block device is the only >>> safe way to reuse the host installation, although it gets a bit >>> complicated if people have multiple devices mounted into the namespace. >> How is -snapshot any different? If the host writes a block after the >> guest has been launched, but before that block was cowed, then the guest >> will see the new block. > Right, thinko - qemu's snapshots are fairly useless due to sitting > ontop of the file to be modified. > >> It could work with a btrfs snapshot, but not everyone uses that. > Or LVM snapshot. Either way, just reusing the root fs without care > is a dumb idea, and I really don't want any tool or script that > encurages such braindead behaviour in the kernel tree. Heh, yeah, the intent was obviously to have a separate rootfs tree somewhere in a directory. But that's not available at first when running this, so I figured for a simple "get me rolling" FAQ directing the guest's rootfs to / at least gets you somewhere (especially when run as user with init=/bin/bash). Alex From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:48171) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNpO1-0008HY-5v for qemu-devel@nongnu.org; Tue, 08 Nov 2011 12:23:02 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1RNpNz-0008CF-SI for qemu-devel@nongnu.org; Tue, 08 Nov 2011 12:23:01 -0500 Received: from cantor2.suse.de ([195.135.220.15]:45449 helo=mx2.suse.de) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1RNpNz-0008BF-C4 for qemu-devel@nongnu.org; Tue, 08 Nov 2011 12:22:59 -0500 Message-ID: <4EB96829.1010709@suse.de> Date: Tue, 08 Nov 2011 18:34:33 +0100 From: Alexander Graf MIME-Version: 1.0 References: <1320543320-32728-1-git-send-email-agraf@suse.de> <4EB93FA4.8020800@redhat.com> <20111108145257.GA10846@infradead.org> <4EB94340.5040205@redhat.com> <20111108145945.GA17842@infradead.org> In-Reply-To: <20111108145945.GA17842@infradead.org> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] KVM: Add wrapper script around QEMU to test kernels List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Christoph Hellwig Cc: Blue Swirl , "kvm@vger.kernel.org list" , qemu-devel Developers , "linux-kernel@vger.kernel.org List" , Pekka Enberg , Avi Kivity , Am?rico Wang , Ingo Molnar , Linus Torvalds On 11/08/2011 03:59 PM, Christoph Hellwig wrote: > On Tue, Nov 08, 2011 at 04:57:04PM +0200, Avi Kivity wrote: >>> Running qemu -snapshot on the actual root block device is the only >>> safe way to reuse the host installation, although it gets a bit >>> complicated if people have multiple devices mounted into the namespace. >> How is -snapshot any different? If the host writes a block after the >> guest has been launched, but before that block was cowed, then the guest >> will see the new block. > Right, thinko - qemu's snapshots are fairly useless due to sitting > ontop of the file to be modified. > >> It could work with a btrfs snapshot, but not everyone uses that. > Or LVM snapshot. Either way, just reusing the root fs without care > is a dumb idea, and I really don't want any tool or script that > encurages such braindead behaviour in the kernel tree. Heh, yeah, the intent was obviously to have a separate rootfs tree somewhere in a directory. But that's not available at first when running this, so I figured for a simple "get me rolling" FAQ directing the guest's rootfs to / at least gets you somewhere (especially when run as user with init=/bin/bash). Alex