linux-kernel - [patch 10/30] x86/cpu/topology: Simplify APIC registration

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Date: Tue, 13 Feb 2024 22:05:47 +0100 (CET)
From: Thomas Gleixner <tglx@...utronix.de>
To: LKML <linux-kernel@...r.kernel.org>
Cc: x86@...nel.org,
 Tom Lendacky <thomas.lendacky@....com>,
 Andrew Cooper <andrew.cooper3@...rix.com>,
 Arjan van de Ven <arjan@...ux.intel.com>,
 Huang Rui <ray.huang@....com>,
 Juergen Gross <jgross@...e.com>,
 Dimitri Sivanich <dimitri.sivanich@....com>,
 Sohil Mehta <sohil.mehta@...el.com>,
 K Prateek Nayak <kprateek.nayak@....com>,
 Kan Liang <kan.liang@...ux.intel.com>,
 Zhang Rui <rui.zhang@...el.com>,
 "Paul E. McKenney" <paulmck@...nel.org>,
 Feng Tang <feng.tang@...el.com>,
 Andy Shevchenko <andy@...radead.org>,
 Michael Kelley <mhklinux@...look.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>
Subject: [patch 10/30] x86/cpu/topology: Simplify APIC registration

From: Thomas Gleixner <tglx@...utronix.de>

Having the same check whether the number of assigned CPUs has reached the
nr_cpu_ids limit twice in the same code path is pointless. Repeating the
information that CPUs are ignored over and over is also pointless noise.

Remove the redundant check and reduce the noise by using a pr_warn_once().

Signed-off-by: Thomas Gleixner <tglx@...utronix.de>

---
 arch/x86/kernel/cpu/topology.c |   23 +++--------------------
 1 file changed, 3 insertions(+), 20 deletions(-)
---

--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -107,14 +107,6 @@ static int allocate_logical_cpuid(u32 ap
 	if (cpu >= 0)
 		return cpu;

-	/* Allocate a new cpuid. */
-	if (nr_logical_cpuids >= nr_cpu_ids) {
-		WARN_ONCE(1, "APIC: NR_CPUS/possible_cpus limit of %u reached. "
-			     "Processor %d/0x%x and the rest are ignored.\n",
-			     nr_cpu_ids, nr_logical_cpuids, apic_id);
-		return -EINVAL;
-	}
-
 	cpuid_to_apicid[nr_logical_cpuids] = apic_id;
 	return nr_logical_cpuids++;
 }
@@ -135,7 +127,7 @@ static void cpu_update_apic(int cpu, u32

 static int generic_processor_info(int apicid)
 {
-	int cpu, max = nr_cpu_ids;
+	int cpu;

 	/* The boot CPU must be set before MADT/MPTABLE parsing happens */
 	if (cpuid_to_apicid[0] == BAD_APICID)
@@ -155,21 +147,12 @@ static int generic_processor_info(int ap
 	}

 	if (num_processors >= nr_cpu_ids) {
-		int thiscpu = max + disabled_cpus;
-
-		pr_warn("APIC: NR_CPUS/possible_cpus limit of %i reached. "
-			"Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
-
+		pr_warn_once("APIC: CPU limit of %d reached. Ignoring further CPUs\n", nr_cpu_ids);
 		disabled_cpus++;
-		return -EINVAL;
+		return -ENOSPC;
 	}

 	cpu = allocate_logical_cpuid(apicid);
-	if (cpu < 0) {
-		disabled_cpus++;
-		return -EINVAL;
-	}
-
 	cpu_update_apic(cpu, apicid);
 	return cpu;
 }