From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:59696) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRKv1-00023N-Un for qemu-devel@nongnu.org; Tue, 09 Sep 2014 08:53:16 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XRKuv-00038M-4C for qemu-devel@nongnu.org; Tue, 09 Sep 2014 08:53:11 -0400 Received: from mx1.redhat.com ([209.132.183.28]:19153) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XRKuu-00037w-SI for qemu-devel@nongnu.org; Tue, 09 Sep 2014 08:53:05 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id s89Cr361009068 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL) for ; Tue, 9 Sep 2014 08:53:03 -0400 Message-ID: <540EF82E.60602@redhat.com> Date: Tue, 09 Sep 2014 06:53:02 -0600 From: Eric Blake MIME-Version: 1.0 References: <20140829160727.69f66ecd@redhat.com> <20140908104217.48f2354a@redhat.com> <20140908153318.GH4297@noname.redhat.com> <20140908125701.3be785e9@redhat.com> <20140909082733.GD4847@noname.str.redhat.com> <540EF48B.5090705@redhat.com> <20140909084353.454cc889@redhat.com> In-Reply-To: <20140909084353.454cc889@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="OWVaOijFkoI8esIQLGXkQMfW4fvbBlaHN" Subject: Re: [Qemu-devel] [PATCH] block: extend BLOCK_IO_ERROR event with nospace indicator List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Luiz Capitulino Cc: Kevin Wolf , fromani@redhat.com, qemu-devel@nongnu.org, armbru@redhat.com This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --OWVaOijFkoI8esIQLGXkQMfW4fvbBlaHN Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 09/09/2014 06:43 AM, Luiz Capitulino wrote: >> Enhancing query-block in addition to the event makes sense, if it is >> easy enough to do. At this point, we are talking about debugging aids= , >> so as long as they are documented appropriately, I won't be too fussy.= >=20 > OK, but I'm wondering if we need to add the string field to both, > BLOCK_IO_ERROR and query-block, or only to one to the other. >=20 > In my opinion, we should only add it to BLOCK_IO_ERROR if libvirt is > going to consume. Otherwise, it makes more sense to add it to query-blo= ck > because that's where we'll meet the user. >=20 > Btw, by "consume" I mean read it and make it available to libvirt clien= ts > so that they can print it to their users. If we don't want libvirt to > consume that field then I think we should only add it to query-block an= d > info block. [For those not aware, qemu built for downstream RHEL already has an error string in the __com.redhat_ namespace; we're trying to figure out what upstream should have so that downstream doesn't have to perpetually maintain an extension] Downstream libvirt does not currently consume any error string. With downstream qemu, the _only_ way to get the error string in the event is to parse libvirt logs, or use upstream libvirt with its backdoor of 'virsh qemu-monitor-event' (through the explicitly unsupported libvirt-qemu.so) to get at the raw event information. Changing libvirt to expose such an error string to the end user would require a new libvirt event number (the existing libvirt event is not extensible), so existing clients would not be able to get at the information without being recompiled to a new libvirt. Since the whole point of this field is for debugging, I think that it is sufficient to add it to JUST query-block, and not to the event. That is, if the app on top of libvirt gets an error, in the common case, they won't care about the message (it won't change how they act), and in the debug case, a developer trying to learn more about what happened can do their own query-block directly (via 'virsh qemu-monitor-command', also in libvirt-qemu.so) rather than trying to wire up libvirt to pass through an error string through a new event. --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --OWVaOijFkoI8esIQLGXkQMfW4fvbBlaHN 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 iQEcBAEBCAAGBQJUDvguAAoJEKeha0olJ0Nqx8QIAIho4QGGLDi07aTk2wFTFL7H xhklYuqcVb8K0q0MMBaub5L5YbAJlGJMxnggbAfj/WVFXqS1ugXxilY3qA8mM7wb sVPxP0jO2ij6/mogrfv0P6WlaaJiyYSm0WECkXT+Po497R02XsyZUR2VHakWTilI YogtFrnb80cV624RrZ0pUATaxdNoe+DFEpyTT0HrKVLM6lFl2tdQWk6v/nyKc/7N ZHcYvCSClRJEdpLYketOdvwNKrI+ntOa4Dj3ajtsm7ADJd+zeZuVn3L0u+IKXZ/L lYLBGr/rDnQAcVm58NJNX+ZJ6vIuwFPehVjnibzUle8Ms3sGrD0QjqMtxOq+HbE= =6etH -----END PGP SIGNATURE----- --OWVaOijFkoI8esIQLGXkQMfW4fvbBlaHN--