From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:51940) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWa47-0001aI-Fm for qemu-devel@nongnu.org; Tue, 14 Jun 2011 16:18:24 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QWa45-0005Rn-SW for qemu-devel@nongnu.org; Tue, 14 Jun 2011 16:18:23 -0400 Received: from mx1.redhat.com ([209.132.183.28]:11479) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QWa45-0005RZ-Di for qemu-devel@nongnu.org; Tue, 14 Jun 2011 16:18:21 -0400 Message-ID: <4DF7C206.2000901@redhat.com> Date: Tue, 14 Jun 2011 14:18:14 -0600 From: Eric Blake MIME-Version: 1.0 References: <4DF762A4.2040503@us.ibm.com> <4DF788AF.3010103@redhat.com> <4DF7BC9F.10506@us.ibm.com> In-Reply-To: <4DF7BC9F.10506@us.ibm.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigC7869B2C9241398EA47B930D" Subject: Re: [Qemu-devel] [libvirt] [PATCH v2] Add support for fd: protocol List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Corey Bryant Cc: libvir-list@redhat.com, Anthony Liguori , qemu-devel@nongnu.org, Tyler C Hicks This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigC7869B2C9241398EA47B930D Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 06/14/2011 01:55 PM, Corey Bryant wrote: >> So we would need something like -drive >> file=3Dfd:4,format=3Dqcow2,backing=3Dfd:5 >> >> and since backing files can be nested, we'd need some way of specifyin= g >> more than one level of backing file. Libvirt already knows how to wal= k >> a chain of backing images in qcow2 files (it has to, in order to set >> sVirt SELinux permissions on all of those files so that qemu can open(= ) >> each file), so it wouldn't be much harder for libvirt to instead do th= e >> open() and pass each fd. >> > Right. So what I was talking about here (and poorly stated) is that > starting Qemu with a copy-on-write image file causes a reopen of the > backing file. In this case you would only be passing the fd of the > copy-on-write file to Qemu. I've fenced that off as unsupported for now= =2E >=20 > I like your approach for passing multiple fds. Do you think backing fil= e > support is needed immediately with this patch? Incremental support is fine by me, but we'll need it sooner or later. And for the nested backing file case, does: -drive file=3Dfd:4,format=3Dqcow2,backing=3Dfd:5,backing=3Dfd:6 work, or would we need: -drive file=3Dfd:4,format=3Dqcow2,backing1=3Dfd:5,backing2=3Dfd:6 That is, can you have more than one backing=3D, or do you need distinct backingN=3D, and if you have to support multiple N, we must make sure the= solution allows arbitrarily deep nesting (or at least as deep as any current limits qemu places on qcow2 backing file nesting). --=20 Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org --------------enigC7869B2C9241398EA47B930D Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iQEcBAEBCAAGBQJN98IGAAoJEKeha0olJ0NqgUMH/1tQQX1VAE8ZoiQKhGr70tRK EAE+5GfBdikMO0YTYJ4rYvSz6jBWRy+ESWcKjOaRLhas0MW87SftDIs+597SVjxr neKaNP0dnjWLRoWDtNbSA2COc1PuDD6mG0SsNFQW7o6zkMcZlO1ExWbOKotp3ETL 0rM/b+MX0cQGeI7TI1+piLgLtx8U9hCR5Fi7P4gepXBLP1TeTibyyijY79onzFe1 kqRNNiIX6Pn4BV8Yyz5wWcxiGDwXZXrbqM/VPYa265zjcdwkSnfAmMRKcQRQmmBS WhBOSz9atP5rSNTLeV60yIjwoGYubi4gq2vWo+CZ+3gZ/sgkT20Bk3KePy0oZBQ= =LNyd -----END PGP SIGNATURE----- --------------enigC7869B2C9241398EA47B930D--