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[Qemu-ppc] [PATCH for-2.9] pseries: Enforce homogeneous threads-per-core

From: David Gibson
Subject: [Qemu-ppc] [PATCH for-2.9] pseries: Enforce homogeneous threads-per-core
Date: Fri, 31 Mar 2017 15:51:44 +1100

For reasons that may be useful in future, CPU core objects, as used on the
pseries machine type have their own nr-threads property, potentially
allowing cores with different numbers of threads in the same system.

If the user/management uses the values specified in query-hotpluggable-cpus
as they're expected to do, this will never matter in pratice.  But that's
not actually enforced - it's possible to manually specify a core with
a different number of threads from that in -smp.  That will confuse the
platform - most immediately, this can be used to create a CPU thread with
index above max_cpus which leads to an assertion failure in

For now, enforce that all cores must have the same, standard, number of
threads.  While we're at it, also enforce that the core ids are correctly
aligned based on that number of threads.

Signed-off-by: David Gibson <address@hidden>
 hw/ppc/spapr_cpu_core.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/hw/ppc/spapr_cpu_core.c b/hw/ppc/spapr_cpu_core.c
index 6883f09..935ee62 100644
--- a/hw/ppc/spapr_cpu_core.c
+++ b/hw/ppc/spapr_cpu_core.c
@@ -167,6 +167,18 @@ static void spapr_cpu_core_realize(DeviceState *dev, Error 
     void *obj;
     int i, j;
+    if (cc->nr_threads != smp_threads) {
+        error_setg(errp,
+                   "Invalid nr-threads=%d of CPU[core-id: %d], must be %d",
+                   cc->nr_threads, cc->core_id, smp_threads);
+        return;
+    }
+    if ((cc->core_id % smp_threads) != 0) {
+        error_setg(errp, "Invalid CPU core-id=%d, must be a multiple of %d",
+                   cc->core_id, smp_threads);
+        return;
+    }
     sc->threads = g_malloc0(size * cc->nr_threads);
     for (i = 0; i < cc->nr_threads; i++) {
         int node_id;

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