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 <stefa...@redhat.com> >>>>>>> Cc: Kevin Wolf <kw...@redhat.com> >>>>>>> Cc: qemu-bl...@nongnu.org >>>>>>> Signed-off-by: Jason Wang <jasow...@redhat.com> >>>>> 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
