linux-kernel - [tip: sched/core] x86/smpboot: moves x86_topology to static initialize and truncate

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Message-ID: <175248423620.406.3273253849830165852.tip-bot2@tip-bot2>
Date: Mon, 14 Jul 2025 09:10:36 -0000
From: "tip-bot2 for Li Chen" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Thomas Gleixner <tglx@...utronix.de>, Li Chen <chenl311@...natelecom.cn>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 K Prateek Nayak <kprateek.nayak@....com>, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: sched/core] x86/smpboot: moves x86_topology to static
 initialize and truncate

The following commit has been merged into the sched/core branch of tip:

Commit-ID:     fbc2010d92e595dc13d8048db2419f963c8cb25e
Gitweb:        https://git.kernel.org/tip/fbc2010d92e595dc13d8048db2419f963c8cb25e
Author:        Li Chen <chenl311@...natelecom.cn>
AuthorDate:    Thu, 10 Jul 2025 18:57:09 +08:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 14 Jul 2025 10:59:34 +02:00

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@...utronix.de>
Signed-off-by: Li Chen <chenl311@...natelecom.cn>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: K Prateek Nayak <kprateek.nayak@....com>
Tested-by: K Prateek Nayak <kprateek.nayak@....com>
Link: https://lore.kernel.org/r/20250710105715.66594-4-me@linux.beauty
---
 arch/x86/kernel/smpboot.c | 34 ++++++++++++++++------------------
 1 file changed, 16 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index 30e6df2..8038286 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -478,32 +478,30 @@ 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);
 }