[Qemu-devel] [RFC 15/15] generate APIC IDs according to CPU topology (v2)

[Eduardo Habkost <ehabkost@redhat.com>]

This keeps compatibility on machine-types pc-1.1 and lower, and prints a
warning in case the requested configuration won't get the correct
topology.

Changes v1 -> v2:
 - Move code to cpu.c
 - keep using cpu_index on *-user
 - Use SMP.contiguous_apic_ids global property
 - Prints warning in case the compatibility mode will expose incorrect
   topology

Signed-off-by: Eduardo Habkost <ehabkost@redhat.com>
---
 hw/pc_piix.c      |  4 ++++
 target-i386/cpu.c | 34 ++++++++++++++++++++++++++++++----
 2 files changed, 34 insertions(+), 4 deletions(-)

diff --git a/hw/pc_piix.c b/hw/pc_piix.c
index 0c0096f..f073916 100644
--- a/hw/pc_piix.c
+++ b/hw/pc_piix.c
@@ -375,6 +375,10 @@ static QEMUMachine pc_machine_v1_2 = {
             .driver   = "qxl",\
             .property = "vgamem_mb",\
             .value    = stringify(8),\
+        },{\
+            .driver   = "SMP",\
+            .property = "contiguous_apic_ids",\
+            .value    = "true",\
         }
 
 static QEMUMachine pc_machine_v1_1 = {
diff --git a/target-i386/cpu.c b/target-i386/cpu.c
index 1703373..ea6c7a7 100644
--- a/target-i386/cpu.c
+++ b/target-i386/cpu.c
@@ -23,9 +23,11 @@
 
 #include "cpu.h"
 #include "kvm.h"
+#include "topology.h"
 
 #ifndef CONFIG_USER_ONLY
-#include "sysemu.h"
+#include "hw/qdev.h"
+#include "cpus.h"
 #endif
 
 #include "qemu-option.h"
@@ -492,13 +494,37 @@ static x86_def_t builtin_x86_defs[] = {
     },
 };
 
+#ifdef CONFIG_USER_ONLY
 unsigned int apic_id_for_cpu(int cpu_index)
 {
-    /* right now APIC ID == CPU index. this will eventually change to use
-     * the CPU topology configuration properly
-     */
+    /* *-user doesn't have any CPU topology settings, just use the CPU index */
     return cpu_index;
 }
+#else
+unsigned int apic_id_for_cpu(int cpu_index)
+{
+    const char *contig;
+    bool is_contiguous;
+    unsigned int correct_id;
+    static bool warned = false;
+
+    /* Global property SMP.contiguous_apic_ids=true will keep compatibility
+     * with the old (broken) behavior when calculating APIC IDs
+     */
+    contig = qemu_global_get("SMP", "contiguous_apic_ids");
+    is_contiguous = contig && !strcmp(contig, "true");
+    correct_id = topo_apicid_for_cpu(smp_cores, smp_threads, cpu_index);
+    if (is_contiguous) {
+        if (cpu_index != correct_id && !warned) {
+            fprintf(stderr, "warning: CPU topology in compatibility mode, it will not match the requested topology\n");
+            warned = true;
+        }
+        return cpu_index;
+    } else {
+        return correct_id;
+    }
+}
+#endif
 
 static int cpu_x86_fill_model_id(char *str)
 {
-- 
1.7.11.2