[Qemu-devel] [PATCH 2/3] target-i386: introduce x86_cpu_nr_apic_ids

["Radim Krčmář" <rkrcmar@redhat.com>]

The number of available APIC IDs depends on chosen topology, because
core/smt choices different from a power of two waste some IDs.

Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>
---
 target-i386/cpu.c | 16 ++++++++++++++++
 target-i386/cpu.h |  1 +
 2 files changed, 17 insertions(+)

diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index e194601..c77ec76 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -2815,6 +2815,22 @@ uint32_t x86_cpu_apic_id_from_index(unsigned int cpu_index)
     }
 }
 
+/* The number of useable APIC IDs based on current topology.
+ *
+ * id_limit is the highest possible APIC ID + 1.
+ */
+unsigned x86_cpu_nr_apic_ids(unsigned id_limit)
+{
+    unsigned package_width;
+
+    if (compat_apic_id_mode)
+        return id_limit;
+
+    package_width = apicid_pkg_width(smp_cores, smp_threads, id_limit);
+
+    return MIN(id_limit, (1 << package_width) * smp_cores * smp_threads);
+}
+
 static void x86_cpu_initfn(Object *obj)
 {
     CPUState *cs = CPU(obj);
diff --git a/target-i386/cpu.h b/target-i386/cpu.h
index 9f01831..367968d 100644
--- a/target-i386/cpu.h
+++ b/target-i386/cpu.h
@@ -1372,6 +1372,7 @@ void x86_cpu_compat_disable_kvm_features(FeatureWord w, uint32_t features);
 const char *get_register_name_32(unsigned int reg);
 
 uint32_t x86_cpu_apic_id_from_index(unsigned int cpu_index);
+unsigned x86_cpu_nr_apic_ids(unsigned id_limit);
 void enable_compat_apic_id_mode(void);
 
 #define APIC_DEFAULT_ADDRESS 0xfee00000
-- 
2.1.0