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. > >>> 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?