From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34702) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZFNfl-0008PW-N9 for qemu-devel@nongnu.org; Wed, 15 Jul 2015 10:28:34 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZFNfk-0007k1-96 for qemu-devel@nongnu.org; Wed, 15 Jul 2015 10:28:33 -0400 Date: Wed, 15 Jul 2015 17:28:24 +0300 From: "Michael S. Tsirkin" Message-ID: <20150715171947-mutt-send-email-mst@redhat.com> References: <1436938201-16766-1-git-send-email-jasowang@redhat.com> <1436938201-16766-4-git-send-email-jasowang@redhat.com> <20150715151941-mutt-send-email-mst@redhat.com> <55A6565C.2060509@redhat.com> <20150715141419.GA15232@redhat.com> <55A66BC9.2000003@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <55A66BC9.2000003@redhat.com> Subject: Re: [Qemu-devel] [PATCH V2 3/5] virtio-blk: disable scsi passthrough by default List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Paolo Bonzini Cc: kwolf@redhat.com, qemu-block@nongnu.org, Jason Wang , qemu-devel@nongnu.org, stefanha@redhat.com, cornelia.huck@de.ibm.com On Wed, Jul 15, 2015 at 04:18:49PM +0200, Paolo Bonzini wrote: > > > On 15/07/2015 16:14, Michael S. Tsirkin wrote: > > On Wed, Jul 15, 2015 at 02:47:24PM +0200, Paolo Bonzini wrote: > >> > >> > >> On 15/07/2015 14:21, Michael S. Tsirkin wrote: > >>>>> Disable scsi passthrough by default since it was incompatible with > >>>>> virtio 1.0. For legacy machine types, keep this on by default. > >>>>> > >>>>> Cc: Stefan Hajnoczi > >>>>> Cc: Kevin Wolf > >>>>> Cc: qemu-block@nongnu.org > >>>>> Signed-off-by: Jason Wang > >>> Seems risky for 2.4. modern is off by default for now. Can't we limit > >>> the change to when modern is enabled? > >> > >> That would have the effect of disabling a feature when you turn on modern. > > > > What's wrong with that? > > Weren't you complaining about it a few hours ago? :) No, I complained about guest driver update disabling it. > >>> I suggested changing this from bool to on/off/auto, and > >>> make auto mean !modern. > >> > >> No, please do it like Jason did. The SCSI feature effectively had to be > >> enabled explicitly already, the requests were marked as unsupported. > > > > I didn't know. How is it enabled? > > It's enabled by default in QEMU, but disabled by default in libvirt. > And it only works if you pass a whole _disk_ (not a partition or logical > volume) to QEMU, which is definitely not the common case. > > It can just be documented in the release notes; the feature is still > available, and libvirt won't be broken because it adds explicitly both > scsi=on and scsi=off. > > Paolo So for libvirt, we don't really care about the default, right? For command line, would it not be friendlier to make it follow the modern flag automatically?