x86/smpboot: moves x86_topology to static initialize and truncate

JIRA: https://issues.redhat.com/browse/RHEL-118964

commit fbc2010
Author: Li Chen <chenl311@chinatelecom.cn>
Date:   Thu Jul 10 18:57:09 2025 +0800

    x86/smpboot: moves x86_topology to static initialize and truncate

    The #ifdeffery and the initializers in build_sched_topology() are just
    disgusting.

    Statically initialize the domain levels in the topology array and let
    build_sched_topology() invalidate the package domain level when NUMA in
    package is available.

    Suggested-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Li Chen <chenl311@chinatelecom.cn>
    Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
    Reviewed-by: K Prateek Nayak <kprateek.nayak@amd.com>
    Tested-by: K Prateek Nayak <kprateek.nayak@amd.com>
    Link: https://lore.kernel.org/r/20250710105715.66594-4-me@linux.beauty

Signed-off-by: Phil Auld <pauld@redhat.com>

Author: auldp

arch/x86/kernel/smpboot.c

@@ -504,32 +504,30 @@ static int x86_cluster_flags(void)
  */
 static bool x86_has_numa_in_package;
 
-static struct sched_domain_topology_level x86_topology[6];
-
-static void __init build_sched_topology(void)
-{
-	int i = 0;
-
-	x86_topology[i++] = SDTL_INIT(cpu_smt_mask, cpu_smt_flags, SMT);
+static struct sched_domain_topology_level x86_topology[] = {
+	SDTL_INIT(cpu_smt_mask, cpu_smt_flags, SMT),
 #ifdef CONFIG_SCHED_CLUSTER
-	x86_topology[i++] = SDTL_INIT(cpu_clustergroup_mask, x86_cluster_flags, CLS);
+	SDTL_INIT(cpu_clustergroup_mask, x86_cluster_flags, CLS),
 #endif
 #ifdef CONFIG_SCHED_MC
-	x86_topology[i++] = SDTL_INIT(cpu_coregroup_mask, x86_core_flags, MC);
+	SDTL_INIT(cpu_coregroup_mask, x86_core_flags, MC),
 #endif
-	/*
-	 * When there is NUMA topology inside the package skip the PKG domain
-	 * since the NUMA domains will auto-magically create the right spanning
-	 * domains based on the SLIT.
-	 */
-	if (!x86_has_numa_in_package)
-		x86_topology[i++] = SDTL_INIT(cpu_cpu_mask, x86_sched_itmt_flags, PKG);
+	SDTL_INIT(cpu_cpu_mask, x86_sched_itmt_flags, PKG),
+	{ NULL },
+};
 
+static void __init build_sched_topology(void)
+{
 	/*
-	 * There must be one trailing NULL entry left.
+	 * When there is NUMA topology inside the package invalidate the
+	 * PKG domain since the NUMA domains will auto-magically create the
+	 * right spanning domains based on the SLIT.
 	 */
-	BUG_ON(i >= ARRAY_SIZE(x86_topology) - 1);
+	if (x86_has_numa_in_package) {
+		unsigned int pkgdom = ARRAY_SIZE(x86_topology) - 2;
 
+		memset(&x86_topology[pkgdom], 0, sizeof(x86_topology[pkgdom]));
+	}
 	set_sched_topology(x86_topology);
 }