[PATCH v2] xen/arm: Fix sibling mask setup to only include online CPUs

[Hirokazu Takahashi <taka@xxxxxxxxxxxxx>]

Populate the CPU sibling map only with CPUs that are brought
online. Currently, all CPUs in cpu_possible_map are added,
which leaves CPUs that failed to boot in the sibling masks and
may lead the scheduler to make incorrect decisions.

Changes in v2:
- Rename init_cpu_sibling_map() to set_cpu_sibling_map() to align
  with x86.
- Use BUG_ON() in set_cpu_sibling_map() to verify that per-cpu
  cpu_sibling_mask and cpu_core_mask are allocated.

Fixes: 701190abb3d5 ("xen/arm: Set correct per-cpu cpu_core_mask")
Signed-off-by: Hirokazu Takahashi <taka@xxxxxxxxxxxxx>
---
 xen/arch/arm/smpboot.c | 19 +++++++++++++++++--
 1 file changed, 17 insertions(+), 2 deletions(-)

diff --git a/xen/arch/arm/smpboot.c b/xen/arch/arm/smpboot.c
index 8c9072f3c1..9237576440 100644
--- a/xen/arch/arm/smpboot.c
+++ b/xen/arch/arm/smpboot.c
@@ -91,15 +91,27 @@ static int setup_cpu_sibling_map(int cpu)
          !zalloc_cpumask_var(&per_cpu(cpu_core_mask, cpu)) )
         return -ENOMEM;
 
+    return 0;
+}
+
+static void set_cpu_sibling_map(int cpu)
+{
+    unsigned int sibling;
+
+    BUG_ON (!per_cpu(cpu_sibling_mask, cpu));
+    BUG_ON (!per_cpu(cpu_core_mask, cpu));
+
     /*
      * Currently we assume there is no multithread and NUMA, so
      * a CPU is a sibling with itself, and the all possible CPUs
      * are supposed to belong to the same socket (NUMA node).
      */
     cpumask_set_cpu(cpu, per_cpu(cpu_sibling_mask, cpu));
-    cpumask_copy(per_cpu(cpu_core_mask, cpu), &cpu_possible_map);
+    cpumask_copy(per_cpu(cpu_core_mask, cpu), &cpu_online_map);
+    cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, cpu));
 
-    return 0;
+    for_each_online_cpu(sibling)
+        cpumask_set_cpu(cpu, per_cpu(cpu_core_mask, sibling));
 }
 
 static void remove_cpu_sibling_map(int cpu)
@@ -314,6 +326,7 @@ smp_prepare_cpus(void)
     if ( rc )
         panic("Unable to allocate CPU sibling/core maps\n");
 
+    set_cpu_sibling_map(0);
 }
 
 /* Boot the current CPU */
@@ -385,6 +398,8 @@ void asmlinkage noreturn start_secondary(void)
 
     set_current(idle_vcpu[cpuid]);
 
+    set_cpu_sibling_map(cpuid);
+
     /* Run local notifiers */
     notify_cpu_starting(cpuid);
     /*
-- 
2.43.0