Re: [Qemu-devel] [PATCH] compat: Use explicit type names on HW_COMPAT_2_6

[Eduardo Habkost <ehabkost@redhat.com>]

On Fri, Jan 04, 2019 at 10:49:19AM +0100, Cornelia Huck wrote:
> On Fri,  4 Jan 2019 01:22:26 -0200
> Eduardo Habkost <ehabkost@redhat.com> wrote:
> 
> > The virtio-pci entries in HW_COMPAT_2_6 had an implicit
> > assumption: that all virtio-pci subclasses support the
> > disable-legacy and disable-modern options.
> > 
> > That assumption was broken by commit f6e501a28ef9 ("virtio:
> > Provide version-specific variants of virtio PCI devices").  This
> > caused QEMU to crash if using the new -non-transitional or
> > -transitional device types:
> > 
> >   $ qemu-system-x86_64 -machine pc-i440fx-2.6 \
> >     -device virtio-net-pci-non-transitional
> >   Unexpected error in object_property_find() at qom/object.c:1092:
> >   qemu-system-x86_64: -device virtio-net-pci-non-transitional: can't apply \
> >   global virtio-pci.disable-modern=on: Property '.disable-modern' not found
> >   Aborted (core dumped)
> > 
> > Replace the virtio-pci.disable-legacy=off and
> > virtio-pci.disable-modern=on entries on HW_COMPAT_2_6 with
> > explicit entries for each generic virtio device type.
> > 
> > The full list of generic virtio device types was extracted by
> > just grepping for ".generic_name".  Note that we don't need to
> > worry about listing new virtio-pci devices in HW_COMPAT_2_6 in
> > the future, because new devices won't require QEMU 2.6
> > compatibility.
> 
> Some of these will not be relevant for 2.6 compat, but better safe than
> sorry :)

Yes.  My first version was based on grepping the v2.6.0 tree, but
then I decided to be safer and grep for ".generic_name" on
qemu.git master.  Just in case somebody is using a v2.7+ device
type with 2.6 machine-types.

> 
> > 
> > This makes the compat entries annoyingly verbose, but is simpler
> > than the alternative of making the virtio-pci type inheritance
> > rules even more complex.
> 
> Maybe also write out explicitly:
> 
> Fixes: f6e501a28ef9 ("virtio: Provide version-specific variants of virtio PCI devices")

Yes, I forgot to do it.  Thanks no noting!

> 
> > 
> > Reported-by: Thomas Huth <thuth@redhat.com>
> > Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
> > ---
> > ---
> >  include/hw/compat.h | 140 +++++++++++++++++++++++++++++++++++++++++++-
> >  1 file changed, 138 insertions(+), 2 deletions(-)
> 
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>

-- 
Eduardo