From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42643) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGJ9B-0000yV-1n for qemu-devel@nongnu.org; Fri, 24 Jun 2016 00:55:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bGJ96-0000af-Sn for qemu-devel@nongnu.org; Fri, 24 Jun 2016 00:55:16 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39768) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bGJ96-0000aX-Kc for qemu-devel@nongnu.org; Fri, 24 Jun 2016 00:55:12 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id E993C3B730 for ; Fri, 24 Jun 2016 04:55:11 +0000 (UTC) Date: Fri, 24 Jun 2016 14:56:51 +1000 From: David Gibson Message-ID: <20160624145651.16a2dbc4@voom.fritz.box> In-Reply-To: <576CADC5.6020602@redhat.com> References: <6a52d9a67cc72abb874c9906df039d11bfe1e18d.1466713052.git.pkrempa@redhat.com> <20160624125617.54dc1fc9@voom.fritz.box> <576CADC5.6020602@redhat.com> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; boundary="Sig_/QeW782phNs0SpBLmF7vwkw+"; protocol="application/pgp-signature" Subject: Re: [Qemu-devel] [PATCH 1/3] qapi: Report support for -device cpu hotplug in query-machines List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake Cc: Peter Krempa , Igor Mammedov , qemu-devel@nongnu.org --Sig_/QeW782phNs0SpBLmF7vwkw+ Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: quoted-printable On Thu, 23 Jun 2016 21:49:25 -0600 Eric Blake wrote: > On 06/23/2016 08:56 PM, David Gibson wrote: > > On Thu, 23 Jun 2016 22:23:23 +0200 > > Peter Krempa wrote: > > =20 > >> For management apps it's very useful to know whether the selected > >> machine type supports cpu hotplug via the new -device approach. Using > >> the presence of 'query-hotpluggable-cpus' is enough for a withess. > >> =20 >=20 > >=20 > > I'd been under the impression that there was a general way of detecting > > the availability of a particular qmp command. Was I mistaken? =20 >=20 > You are correct - query-commands says whether 'query-hotpluggable-cpus' > exists as a command. But that is insufficient. See my review, or the > v2 patch, where the above poor wording was corrected to say what was > really meant: knowing whether query-hotpluggable-cpus exists is > insufficient to tell you whether a given cpu type can be hotplugged. So > adding one more piece of witness (for every type of cpu supported, we > also advertise if it is hotpluggable) is enough for libvirt to > efficiently take advantage of the new query-hotpluggable-cpus command. Ah, right. Or to put it another way, the availability of query-hotpluggable-cpus is global across qemu, whereas actually being able to use it for hotplug is per machine type. Would it be possible to do this instead by attempting to invoke query-hopluggable-cpus and seeing if it returns any information? --=20 David Gibson Senior Software Engineer, Virtualization, Red Hat --Sig_/QeW782phNs0SpBLmF7vwkw+ Content-Type: application/pgp-signature Content-Description: OpenPGP digital signature -----BEGIN PGP SIGNATURE----- Version: GnuPG v2 iQIcBAEBCAAGBQJXbL2TAAoJEGw4ysog2bOSr+QQAJPYsIE7/8Z9FGkwgn+M8sh1 Ys1+6MvBzVZgUyDxlCTBV7HVlcmjP7TTdujJEuijLgGcVVrMSkoHYMzj2qLwNolH zPikK8ujq2/1n/1oPphkD6KizhWfPcbM1jNbJZFjx7SqNMpWk4LfrkACa5y4oOwz JiLuYI0NHvZqArYvR2hFRwy0oY2t1wuSNXSY78wWH7b/yXy4mbxXnR+55U37V5/E /uefr00I3jBjOTysqJeYb7THjD1anHkN+bCmpKbeKRPYSrHTP7vRg3cY8quu4g+v fQHfNouH8ImZYuB3Mlzx4oZP48PvVmP7JU6VEFeDRcI0pilmay9cd671P/yM9jYI GjqXurqjdUyLv/p4xFnLT3nm51KVlQt1ZxKIIiNSGrBiGbpCIqFIroKcEcYZdf2p LLQ9PLAloR4IjbqgagSPjBePnXhwPg17FB+l5sw3/SU7yUbrfD0nwRpqdN4POpXh Dl8qnquCkk+CFrjhCY7SJo2kxRWvQTaQW9EAXmsoBEBriP7AKf208VArlYOOLo50 6E0y0GLwp16DRapAUIuiRdtrgYIITZ4ncNj1rdLN/cZTAkMJHS/CUM9xtTuAmU/M 2yuwb7yr+RT+ljbOYw/X17Sl2R8zYEz3ukGjJU0d2v/vLvsunpxdT94h/iZ/LJpY BfZwAPkTMay/IlSGTQG5 =09fw -----END PGP SIGNATURE----- --Sig_/QeW782phNs0SpBLmF7vwkw+--