On Fri, Feb 07, 2020 at 03:30:54PM +1100, David Gibson 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.
It's worth noting in the commit log that this disables support for guests older than Linux 4.0. > > 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 c9b2e0a5e0..216d3b34dc 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" > > @@ -4512,7 +4513,14 @@ static const TypeInfo spapr_machine_info = { > */ > static void spapr_machine_5_0_class_options(MachineClass *mc) > { > - /* Defaults for the latest behaviour inherited from the base class */ > + /* Most defaults for the latest behaviour are inherited from the > + * base class, but we need to override the (non ppc specific) > + * default behaviour for virtio */ > + static GlobalProperty compat[] = { > + { TYPE_VIRTIO_PCI, "disable-legacy", "on", }, > + }; > + > + compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat)); > } > > DEFINE_SPAPR_MACHINE(5_0, "5.0", true); So this sets the defaults, right? Problem is we'll then need to remember to carry this in the latest call. If we forget we get a mess. How about adding a call to e.g. spapr_machine_latest_class_options in DEFINE_SPAPR_MACHINE? Then spapr_machine_latest_class_options can set the per-machine defaults. I send a patch for this: [PATCH] ppc: function to setup latest class options feel free to reuse. > @@ -4523,11 +4531,15 @@ DEFINE_SPAPR_MACHINE(5_0, "5.0", true); > static void spapr_machine_4_2_class_options(MachineClass *mc) > { > SpaprMachineClass *smc = SPAPR_MACHINE_CLASS(mc); > + static GlobalProperty compat[] = { > + { TYPE_VIRTIO_PCI, "disable-legacy", "auto" }, > + }; > > spapr_machine_5_0_class_options(mc); > compat_props_add(mc->compat_props, hw_compat_4_2, hw_compat_4_2_len); > smc->default_caps.caps[SPAPR_CAP_CCF_ASSIST] = SPAPR_CAP_OFF; > smc->default_caps.caps[SPAPR_CAP_FWNMI_MCE] = SPAPR_CAP_OFF; > + compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat)); > } > > DEFINE_SPAPR_MACHINE(4_2, "4.2", false); > -- > 2.24.1