From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:41827) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzZwq-0003I0-5q for qemu-devel@nongnu.org; Tue, 24 Jun 2014 19:16:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1WzZwl-0005rU-8l for qemu-devel@nongnu.org; Tue, 24 Jun 2014 19:16:20 -0400 Received: from mx1.redhat.com ([209.132.183.28]:3839) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1WzZwl-0005rO-14 for qemu-devel@nongnu.org; Tue, 24 Jun 2014 19:16:15 -0400 Message-ID: <53AA06BC.5090604@redhat.com> Date: Tue, 24 Jun 2014 17:16:12 -0600 From: Eric Blake MIME-Version: 1.0 References: <53A9EDAC.6040808@theiggy.com> In-Reply-To: <53A9EDAC.6040808@theiggy.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="kaON5VThEl5KQ7SOBnAUJ9JMsFR8uURF3" Subject: Re: [Qemu-devel] Live Migration with different block devices List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Brian Jackson , Xiongzi Ge , qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --kaON5VThEl5KQ7SOBnAUJ9JMsFR8uURF3 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 06/24/2014 03:29 PM, Brian Jackson wrote: >=20 >=20 > On 6/24/2014 2:22 PM, Xiongzi Ge wrote: >> Hi, >> >> >> When I do live migration, in the source and destination host, there ar= e >> different block devices, but qemu can not detect this. I used virtio >> as the >> driver in kvm and in the vdi device in the guest is /dev/vda. So,=20 >> the vm >> guest can read different data from the same /dev/vda device. I am >> studying >> this code to let qemu understand that, this is a new device. >> >> Does qemu recognize different block devices after live migration? >=20 > You aren't supposed to have different command line options when live > migrating (with the exception of -incoming if you migrate that way). So= > whatever you are trying to do is unsupported. Caveat - it IS supported to change command line options for things that do NOT impact guest ABI. For example, if you have /path/to/file as the host location containing the guest image on the source, but /other/path/file as the location on the destination, you CAN rewrite that parameter (and in fact, libvirt DOES supporting the rewrite such parameters if you use the 'virsh migrate --xml' option - after first proving that your changes do not affect guest ABI). But the onus is on you to ensure that src:/path/to/file and dst:/other/path/file have the SAME guest-visible contents at the time of the migration (this generally requires that the two names be mappings to the same underlying network resource; you can get trickier, but it starts to be at your peril, because the guest is hosed if the two files differ in guest contents). --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --kaON5VThEl5KQ7SOBnAUJ9JMsFR8uURF3 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 Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJTqga8AAoJEKeha0olJ0Nqq9kIAID3PpFOv503q1nYVT4IWb3F ykGdOsSgcs5/9qE0nK+csAYXteO5A0Rc7pEH0sHy05pYduwg/rh/U9+AQV0lcv0m quiphZ5eMq5A8HxklcQq2ggUx5St3nwcczufo8J2TcMFali33IamT3KRXwRwvvNi pI/fdrcUVh5ZUnR4rqugJ2QJfy1QDDJ/UFnuIlrmvvoAWzIAQ0GyWJHB4Vwv1Nnl F5LAnoS3whIY6J58ROOXu+yaaW1LisCwxXjn+2DYo2vEyr5nD72j7iA8I/NzFPd/ FVFn/rzkDUEcYgGlx/2w8g5hVPBIi5M4DucAXJd7rw+/v3c3ATPbZ078jJ28c5g= =5cSr -----END PGP SIGNATURE----- --kaON5VThEl5KQ7SOBnAUJ9JMsFR8uURF3--