From 459264ef24cf2d409b8baf2047fa86e697d6e9ab Mon Sep 17 00:00:00 2001 From: David Gibson Date: Tue, 23 May 2017 16:33:06 +1000 Subject: [PATCH] pseries: Restore support for total vcpus not a multiple of threads-per-core for old machine types 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 Reviewed-by: Laurent Vivier Reviewed-by: Greg Kurz Tested-by: Greg Kurz --- 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 c92d269027..bcb0e184a0 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;