From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pekka Enberg Subject: Re: linux next: Native Linux KVM tool inclusion request Date: Wed, 24 Aug 2011 12:19:12 +0300 Message-ID: <4E54C210.1030204@kernel.org> References: <1314044960.3668.9.camel@lappy> <20110823003925.GA30253@infradead.org> <4E54B6E2.2030203@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from mail-ey0-f174.google.com ([209.85.215.174]:43574 "EHLO mail-ey0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751393Ab1HXJTS (ORCPT ); Wed, 24 Aug 2011 05:19:18 -0400 In-Reply-To: <4E54B6E2.2030203@redhat.com> Sender: linux-next-owner@vger.kernel.org List-ID: To: Avi Kivity Cc: Christoph Hellwig , Sasha Levin , Stephen Rothwell , linux-kernel , Ingo Molnar , Andrew Morton , Linus Torvalds , linux-next@vger.kernel.org On 8/24/11 11:31 AM, Avi Kivity wrote: > On 08/23/2011 08:08 AM, Pekka Enberg wrote: >> As for changes, we've implemented rootfs over 9p with "kvm run" >> booting to host filesystem "/bin/sh" by default. > > Isn't this dangerous? Users expect virtualization to land them in > sandbox, but here an rm -rf / in the guest will happily junk the host > filesystem. Not really because I never run the tool as root. However, you're right that we should not default to /bin/sh if you're root. >> It still needs some >> work and we hope to enable networking too. We also have patches to use >> overlayfs so that the guest is able to use host filesystem in >> copy-on-write manner. > > Still dangerous (but just to the guest), since it's not a true > snapshot. If the host filesystem changes underneath the guest, it > will see partial and incoherent updates. Copy-on-write only works if > the host filesystem doesn't change. That's a generic problem with overlayfs based solutions, isn't it? We're planning to use copy-on-write only on files that aren't supposed to change that often - like /usr and /lib. I suppose we should force shared files to be read-only in the guest. Pekka