On Thu, Feb 13, 2020 at 03:34:25PM +0100, Greg Kurz wrote:
> On Thu, 13 Feb 2020 11:58:36 +1100
> David Gibson <da...@gibson.dropbear.id.au> wrote:
>
> > PAPR specifies a kind of odd, paravirtualized PCI bus, which looks to
> > the guess mostly like classic PCI, even if some of the individual
> > devices on the bus are PCI Express. One consequence of that is that
> > virtio-pci devices still default to being in transitional mode, though
> > legacy mode is now disabled by default on current q35 x86 machine
> > types.
> >
> > Legacy mode virtio devices aren't really necessary any more, and are
> > causing some problems for future changes. Therefore, for the
> > pseries-5.0 machine type (and onwards), switch to modern-only
> > virtio-pci devices by default.
> >
> > This does mean we no longer support guest kernels prior to 4.0, unless
> > they have modern virtio support backported (which some distro kernels
> > like that in RHEL7 do).
> >
> > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> > ---
> > hw/ppc/spapr.c | 14 +++++++++++++-
> > 1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > index cb220fde45..6e1e467cc6 100644
> > --- a/hw/ppc/spapr.c
> > +++ b/hw/ppc/spapr.c
> > @@ -65,6 +65,7 @@
> >
> > #include "hw/pci/pci.h"
> > #include "hw/scsi/scsi.h"
> > +#include "hw/virtio/virtio-pci.h"
> > #include "hw/virtio/virtio-scsi.h"
> > #include "hw/virtio/vhost-scsi-common.h"
> >
> > @@ -4567,7 +4568,14 @@ static void
> > spapr_machine_latest_class_options(MachineClass *mc)
> > */
> > static void spapr_machine_5_0_class_options(MachineClass *mc)
> > {
> > - /* Defaults for the latest behaviour inherited from the base class */
>
> Hmm... and so it seems we still have to carry this around when we
> add a new machine version. At least, that's what I had to do when
> adding a dummy 5.1 machine. This is because it is the old machine
> type that calls the class_options() function of the new one, not
> the other way around.
Uh.. no. It can just go in latest_class_options. I thought I'd
already moved it there, but obviously not. I've fixed that up for the
next spin.
> I was thinking about adapting Michael's patch. Instead of having
> a class_options() function that we only call for the latest
> machine type, we need a function that sets the default behaviour
> and call it for all machine types (which can still change the
> behaviour in their own class_options() function).
This will be confusing in a different way. It will reset the default
options on each of the chained old machine types, which means anything
set in the "default" options needs to be overriden in *all* old
machine types that don't want it, not just the latest which doesn't
want it.
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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