| Message ID | 1477825928-10803-18-git-send-email-david@gibson.dropbear.id.au |
|---|---|
| State | New |
| Headers | show |
On Sun, Oct 30, 2016 at 10:12:08PM +1100, David Gibson wrote: > Currently, the pseries machine defaults to running in the "raw" mode of > whatever the CPU version is - that is, without any compatibility options > enabled in the CPU. > > However, migration is only really safe in "raw" mode if source and > destination have exactly the same cpu model. Since HV KVM exposes the > version of the host CPU to the guest, that means "raw" migration between > hosts with different minor revisions isn't strictly safe, although it > generally works in practice. > > To allow this sort of migration in a more clearly defined way, instead > default to running in POWER8 compatibility mode - if an older CPU is used > that will automatically be downgraded to the higest available compatibility > mode. > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> Ugh, sorry. When I said minimally tested I did mean that it passed make check, but unfortunately I was sloppy and this last patch breaks a bunch of stuff. > --- > hw/ppc/spapr.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index 2aa0900..8c18dc8 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -2194,6 +2194,7 @@ static void spapr_machine_initfn(Object *obj) > " (required for memory hot-unplug support)", > NULL); > > + spapr->max_compat_pvr = CPU_POWERPC_LOGICAL_2_07; /* POWER8 */ > object_property_add(obj, "max-cpu-compat", "str", > ppc_compat_prop_get, ppc_compat_prop_set, > NULL, &spapr->max_compat_pvr, &error_fatal);
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c index 2aa0900..8c18dc8 100644 --- a/hw/ppc/spapr.c +++ b/hw/ppc/spapr.c @@ -2194,6 +2194,7 @@ static void spapr_machine_initfn(Object *obj) " (required for memory hot-unplug support)", NULL); + spapr->max_compat_pvr = CPU_POWERPC_LOGICAL_2_07; /* POWER8 */ object_property_add(obj, "max-cpu-compat", "str", ppc_compat_prop_get, ppc_compat_prop_set, NULL, &spapr->max_compat_pvr, &error_fatal);
Currently, the pseries machine defaults to running in the "raw" mode of whatever the CPU version is - that is, without any compatibility options enabled in the CPU. However, migration is only really safe in "raw" mode if source and destination have exactly the same cpu model. Since HV KVM exposes the version of the host CPU to the guest, that means "raw" migration between hosts with different minor revisions isn't strictly safe, although it generally works in practice. To allow this sort of migration in a more clearly defined way, instead default to running in POWER8 compatibility mode - if an older CPU is used that will automatically be downgraded to the higest available compatibility mode. Signed-off-by: David Gibson <david@gibson.dropbear.id.au> --- hw/ppc/spapr.c | 1 + 1 file changed, 1 insertion(+)