From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:36438) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZZZox-00085o-N9 for qemu-devel@nongnu.org; Wed, 09 Sep 2015 03:29:32 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZZZos-0007Sv-Ns for qemu-devel@nongnu.org; Wed, 09 Sep 2015 03:29:31 -0400 References: <1441761736-32030-1-git-send-email-david@gibson.dropbear.id.au> <55EFD0DE.1050001@redhat.com> <20150909071934.GD17641@voom.redhat.com> From: Thomas Huth Message-ID: <55EFDFCE.2040609@redhat.com> Date: Wed, 9 Sep 2015 09:29:18 +0200 MIME-Version: 1.0 In-Reply-To: <20150909071934.GD17641@voom.redhat.com> Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="b6SXufUPLSF9i21h2GkSiHTUm39nf7im1" Subject: Re: [Qemu-devel] [PATCH] spapr: Reduce advertised max LUNs for spapr_vscsi List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: David Gibson Cc: lvivier@redhat.com, pbonzini@redhat.com, qemu-ppc@nongnu.org, qemu-devel@nongnu.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --b6SXufUPLSF9i21h2GkSiHTUm39nf7im1 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable On 09/09/15 09:19, David Gibson wrote: > On Wed, Sep 09, 2015 at 08:25:34AM +0200, Thomas Huth wrote: >> On 09/09/15 03:22, David Gibson wrote: >>> The implementation of the PAPR paravirtual SCSI adapter currently >>> allows up to 32 LUNs (max_lun =3D=3D 31). However the adapter isn't = really >>> designed to support lots of devices - the PowerVM implementation only= >>> ever puts one disk per vSCSI controller. >> >> Do you know how many LUNs are advertised by PowerVM? >=20 > Well, what do you mean by "advertised". AFAIK from the point of view > of the guest, the number of LUNs is advertised per-target, not per > controller. I mean, what's the highest LUN number that can be seen by a guest under PowerVM? Is it always using only one LUN per controller, or is there a way to change the amount of LUNs? (Sorry if I ask dumb questions ... I do not have much experience with PowerVM yet) >>> More specifically, the Linux guest side vscsi driver (the only one we= >>> really care about) is hardcoded to allow a maximum of 8 LUNs. >> >> So what about changing the vscsi driver in Linux instead to support mo= re >> LUNs? >=20 > Doesn't help for existing guests. Basically what I'm trying to > achieve is for qemu to reject up-front configurations that are > unlikely to actually work in the guest. I just wonder whether it makes sense to change the guest instead. In the future, if we ever have guests that support more LUNs than 8 (maybe some non-Linux guests like FreeBSD?), we've got to change QEMU back again... OTOH, since this is just a one-line fix, it's likely ok to limit this to 8 now - it's easy to revert if we ever need to, so I'm fine with that change, I just wanted to discuss the other possibilites. Thomas --b6SXufUPLSF9i21h2GkSiHTUm39nf7im1 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v2.0.22 (GNU/Linux) iQIcBAEBAgAGBQJV79/SAAoJEC7Z13T+cC21U/4QAIUupEATQSR27Msva6KyVoSa L0eVzNT5SGm/96TrxHy1ArNxz1jAy99yBh9+D1tZO4q5TphlSopYngTv4Bstiryt agtzH/2ShuJDLLoOB0b1pJWvco5Ctn4Jy8RGVvOpFDYeb5YMA17/pdxBy6UDfWgQ oY6/wyHNwSKZVC3Weg/xBmgkfpkfprt4QGfe2ai3HAHvB7zl7Sh561Slbg+ckEmZ EJFlE0qh348z8aXksGgFzb6mbvVZX7JF7WLy6eGZSnLINSLeODgsUn+r36L4YxiX m9qQl7h+/U/3HON/Ga8trvKVJKPkXB3Us/4jydVTHF4bYsFUcKELiezvKnvW6fap UwXvuwe3uuSLSfNaqJAghYe/41xwDYdN3YscSsNJtL3jiJTM5W7XOypIlZa226/J efZJVlTHU2pq23qK2SZqE0MQzVDbkgv3IDKVzrWZEwBq2uaDsfgLpTUz5T3fDxin PxUdrFT84JPaIStpE8Udd8Jnc1H5ysvGi4sqa0hngHkXGimgBtGLqpZjJB1e64Jy 4mV/TuKKQVF9JdDgtWxnHkHBnHmruDnQ1+aKd/4LOEtQaI0/KwZNANaJb4wtG5tG L8xaqukXSg0K+VdrzRCY51grhdMNRDittxmj9oaqmyvvP80hmpeJskN5xa+DSdux YWDG+jw/JH2Bv7Mz/uBd =LWO+ -----END PGP SIGNATURE----- --b6SXufUPLSF9i21h2GkSiHTUm39nf7im1--