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.
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).
Something like the following:
-----------------------------------------------------------------------------
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index 828e2cc1359a..27e6f79ddc40 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -4559,10 +4559,9 @@ static const TypeInfo spapr_machine_info = {
},
};
-static void spapr_machine_latest_class_options(MachineClass *mc)
+static void spapr_machine_default_class_options(MachineClass *mc)
{
- mc->alias = "pseries";
- mc->is_default = 1;
+ /* Override non ppc specific default behaviour here. */
}
#define DEFINE_SPAPR_MACHINE(suffix, verstr, latest) \
@@ -4570,9 +4569,11 @@ static void
spapr_machine_latest_class_options(MachineClass *mc)
void *data) \
{ \
MachineClass *mc = MACHINE_CLASS(oc); \
+ spapr_machine_default_class_options(mc); \
spapr_machine_##suffix##_class_options(mc); \
if (latest) { \
- spapr_machine_latest_class_options(mc); \
+ mc->alias = "pseries"; \
+ mc->is_default = 1; \
} \
} \
static const TypeInfo spapr_machine_##suffix##_info = { \
@@ -4591,7 +4592,11 @@ 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 */
+ /*
+ * Most defaults for the latest behaviour are inherited from the
+ * base class. If a non ppc specific default behaviour needs to
+ * be overriden, do it in spapr_machine_latest_class_options().
+ */
}
DEFINE_SPAPR_MACHINE(5_0, "5.0", true);
-----------------------------------------------------------------------------
With the above applied...
> + /* 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));
... this change would just need to move to spapr_machine_default_class_options()
and any need machine type would have it automatically.
Makes sense ?
> }
>
> DEFINE_SPAPR_MACHINE(5_0, "5.0", true);
> @@ -4578,12 +4586,16 @@ 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;
> mc->nvdimm_supported = false;
> + compat_props_add(mc->compat_props, compat, G_N_ELEMENTS(compat));
> }
>
> DEFINE_SPAPR_MACHINE(4_2, "4.2", false);
