i386/cpu: add has_caches flag to check smp_cache configuration

Add has_caches flag to SMPCompatProps, which helps in avoiding
extra checks for every single layer of caches in x86 (and ARM in
future).

Signed-off-by: Alireza Sanaee <alireza.sanaee@huawei.com>
Signed-off-by: Zhao Liu <zhao1.liu@intel.com>
Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Link: https://lore.kernel.org/r/20250110145115.1574345-6-zhao1.liu@intel.com
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

3 files changed, 10 insertions, 6 deletions

diff --git a/hw/core/machine-smp.c b/hw/core/machine-smp.c
index 4e020c3..0be0ac0 100644
--- a/hw/core/machine-smp.c
+++ b/hw/core/machine-smp.c
@@ -332,6 +332,8 @@ bool machine_parse_smp_cache(MachineState *ms,
             return false;
         }
     }
+
+    mc->smp_props.has_caches = true;
     return true;
 }
 
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 9360d1c..f22b2e7 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -156,6 +156,8 @@ typedef struct {
  * @modules_supported - whether modules are supported by the machine
  * @cache_supported - whether cache (l1d, l1i, l2 and l3) configuration are
  *                    supported by the machine
+ * @has_caches - whether cache properties are explicitly specified in the
+ *               user provided smp-cache configuration
  */
 typedef struct {
     bool prefer_sockets;
@@ -166,6 +168,7 @@ typedef struct {
     bool drawers_supported;
     bool modules_supported;
     bool cache_supported[CACHE_LEVEL_AND_TYPE__MAX];
+    bool has_caches;
 } SMPCompatProps;
 
 /**
diff --git a/target/i386/cpu.c b/target/i386/cpu.c
index 005ca42..2f9c604 100644
--- a/target/i386/cpu.c
+++ b/target/i386/cpu.c
@@ -8203,13 +8203,12 @@ static void x86_cpu_realizefn(DeviceState *dev, Error **errp)
 
 #ifndef CONFIG_USER_ONLY
     MachineState *ms = MACHINE(qdev_get_machine());
+    MachineClass *mc = MACHINE_GET_CLASS(ms);
 
-    /*
-     * TODO: Add a SMPCompatProps.has_caches flag to avoid useless updates
-     * if user didn't set smp_cache.
-     */
-    if (!x86_cpu_update_smp_cache_topo(ms, cpu, errp)) {
-        return;
+    if (mc->smp_props.has_caches) {
+        if (!x86_cpu_update_smp_cache_topo(ms, cpu, errp)) {
+            return;
+        }
     }
 
     qemu_register_reset(x86_cpu_machine_reset_cb, cpu);