From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Subject: Re: [PATCH] KVM: Add wrapper script around QEMU to test kernels Date: Tue, 8 Nov 2011 09:59:45 -0500 Message-ID: <20111108145945.GA17842@infradead.org> References: <1320543320-32728-1-git-send-email-agraf@suse.de> <4EB93FA4.8020800@redhat.com> <20111108145257.GA10846@infradead.org> <4EB94340.5040205@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Christoph Hellwig , Alexander Graf , 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 To: Avi Kivity Return-path: Received: from 173-166-109-252-newengland.hfc.comcastbusiness.net ([173.166.109.252]:54207 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755015Ab1KHO7v (ORCPT ); Tue, 8 Nov 2011 09:59:51 -0500 Content-Disposition: inline In-Reply-To: <4EB94340.5040205@redhat.com> Sender: kvm-owner@vger.kernel.org List-ID: 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.