From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:40115) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZFNwr-0006m7-7j for qemu-devel@nongnu.org; Wed, 15 Jul 2015 10:46:18 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZFNwj-000825-Bt for qemu-devel@nongnu.org; Wed, 15 Jul 2015 10:46:13 -0400 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> <20150715171947-mutt-send-email-mst@redhat.com> From: Paolo Bonzini Message-ID: <55A67220.1020709@redhat.com> Date: Wed, 15 Jul 2015 16:45:52 +0200 MIME-Version: 1.0 In-Reply-To: <20150715171947-mutt-send-email-mst@redhat.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit 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: "Michael S. Tsirkin" Cc: kwolf@redhat.com, qemu-block@nongnu.org, Jason Wang , qemu-devel@nongnu.org, stefanha@redhat.com, cornelia.huck@de.ibm.com On 15/07/2015 16:28, Michael S. Tsirkin wrote: > 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. Ah, sorry for the confusion. >>>>> 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. > > 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? I wouldn't mind if we grabbed the occasion to disable it altogether. However, that would indeed work as well. Paolo