As of pseries-2.7 and later, we require the total number of guest vcpus to
be a multiple of the threads-per-core. pseries-2.6 and earlier machine
types, however, are supposed to allow this for the sake of migration from
old qemu versions which allowed this.
Unfortunately, 8149e29 "pseries: Enforce homogeneous threads-per-core"
broke this by not considering the old machine type case. This fixes it by
only applying the check when the machine type supports hotpluggable cpus.
By not-entirely-coincidence, that corresponds to the same time when we
started enforcing total threads being a multiple of threads-per-core.
Fixes: 8149e2992f7811355cc34721b79d69d1a3a667dd
Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
---
hw/ppc/spapr.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index c92d269..bcb0e18 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -2863,7 +2863,13 @@ static void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev,
goto out;
}
- if (cc->nr_threads != smp_threads) {
+ /*
+ * In general we should have homogeneous threads-per-core, but old
+ * (pre hotplug support) machine types allow the last core to have
+ * reduced threads as a compatibility hack for when we allowed
+ * total vcpus not a multiple of threads-per-core.
+ */
+ if (mc->has_hotpluggable_cpus && (cc->nr_threads != smp_threads)) {
error_setg(errp, "invalid nr-threads %d, must be %d",
cc->nr_threads, smp_threads);
return;
--
2.9.4
On 23/05/2017 08:36, David Gibson wrote: > As of pseries-2.7 and later, we require the total number of guest vcpus to > be a multiple of the threads-per-core. pseries-2.6 and earlier machine > types, however, are supposed to allow this for the sake of migration from > old qemu versions which allowed this. > > Unfortunately, 8149e29 "pseries: Enforce homogeneous threads-per-core" > broke this by not considering the old machine type case. This fixes it by > only applying the check when the machine type supports hotpluggable cpus. > By not-entirely-coincidence, that corresponds to the same time when we > started enforcing total threads being a multiple of threads-per-core. > > Fixes: 8149e2992f7811355cc34721b79d69d1a3a667dd > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > --- > hw/ppc/spapr.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index c92d269..bcb0e18 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -2863,7 +2863,13 @@ static void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev, > goto out; > } > > - if (cc->nr_threads != smp_threads) { > + /* > + * In general we should have homogeneous threads-per-core, but old > + * (pre hotplug support) machine types allow the last core to have > + * reduced threads as a compatibility hack for when we allowed > + * total vcpus not a multiple of threads-per-core. > + */ > + if (mc->has_hotpluggable_cpus && (cc->nr_threads != smp_threads)) { > error_setg(errp, "invalid nr-threads %d, must be %d", > cc->nr_threads, smp_threads); > return; > Reviewed-by: Laurent Vivier <lvivier@redhat.com>
On Tue, 23 May 2017 16:36:45 +1000 David Gibson <david@gibson.dropbear.id.au> wrote: > As of pseries-2.7 and later, we require the total number of guest vcpus to > be a multiple of the threads-per-core. pseries-2.6 and earlier machine > types, however, are supposed to allow this for the sake of migration from > old qemu versions which allowed this. > > Unfortunately, 8149e29 "pseries: Enforce homogeneous threads-per-core" > broke this by not considering the old machine type case. This fixes it by > only applying the check when the machine type supports hotpluggable cpus. > By not-entirely-coincidence, that corresponds to the same time when we > started enforcing total threads being a multiple of threads-per-core. > > Fixes: 8149e2992f7811355cc34721b79d69d1a3a667dd > > Signed-off-by: David Gibson <david@gibson.dropbear.id.au> > --- Reviewed-by: Greg Kurz <groug@kaod.org> and Tested-by: Greg Kurz <groug@kaod.org> > hw/ppc/spapr.c | 8 +++++++- > 1 file changed, 7 insertions(+), 1 deletion(-) > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c > index c92d269..bcb0e18 100644 > --- a/hw/ppc/spapr.c > +++ b/hw/ppc/spapr.c > @@ -2863,7 +2863,13 @@ static void spapr_core_pre_plug(HotplugHandler *hotplug_dev, DeviceState *dev, > goto out; > } > > - if (cc->nr_threads != smp_threads) { > + /* > + * In general we should have homogeneous threads-per-core, but old > + * (pre hotplug support) machine types allow the last core to have > + * reduced threads as a compatibility hack for when we allowed > + * total vcpus not a multiple of threads-per-core. > + */ > + if (mc->has_hotpluggable_cpus && (cc->nr_threads != smp_threads)) { > error_setg(errp, "invalid nr-threads %d, must be %d", > cc->nr_threads, smp_threads); > return;
© 2016 - 2024 Red Hat, Inc.