linux-kernel - [tip: x86/urgent] x86/cpu/topology: Remove limit of CPUs due to disabled IO/APIC

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Message-ID: <173341148312.412.2519390948477165074.tip-bot2@tip-bot2>
Date: Thu, 05 Dec 2024 15:11:23 -0000
From: "tip-bot2 for Fernando Fernandez Mancera" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: Fernando Fernandez Mancera <ffmancera@...eup.net>,
 Thomas Gleixner <tglx@...utronix.de>, stable@...r.kernel.org, x86@...nel.org,
 linux-kernel@...r.kernel.org
Subject: [tip: x86/urgent] x86/cpu/topology: Remove limit of CPUs due to
 disabled IO/APIC

The following commit has been merged into the x86/urgent branch of tip:

Commit-ID:     73da582a476ea6e3512f89f8ed57dfed945829a2
Gitweb:        https://git.kernel.org/tip/73da582a476ea6e3512f89f8ed57dfed945829a2
Author:        Fernando Fernandez Mancera <ffmancera@...eup.net>
AuthorDate:    Mon, 02 Dec 2024 14:58:45 
Committer:     Thomas Gleixner <tglx@...utronix.de>
CommitterDate: Thu, 05 Dec 2024 14:43:32 +01:00

x86/cpu/topology: Remove limit of CPUs due to disabled IO/APIC

The rework of possible CPUs management erroneously disabled SMP when the
IO/APIC is disabled either by the 'noapic' command line parameter or during
IO/APIC setup. SMP is possible without IO/APIC.

Remove the ioapic_is_disabled conditions from the relevant possible CPU
management code paths to restore the orgininal behaviour.

Fixes: 7c0edad3643f ("x86/cpu/topology: Rework possible CPU management")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@...eup.net>
Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
Cc: stable@...r.kernel.org
Link: https://lore.kernel.org/all/20241202145905.1482-1-ffmancera@riseup.net
---
 arch/x86/kernel/cpu/topology.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 621a151..b2e313e 100644
--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -428,8 +428,8 @@ void __init topology_apply_cmdline_limits_early(void)
 {
 	unsigned int possible = nr_cpu_ids;
 
-	/* 'maxcpus=0' 'nosmp' 'nolapic' 'disableapic' 'noapic' */
-	if (!setup_max_cpus || ioapic_is_disabled || apic_is_disabled)
+	/* 'maxcpus=0' 'nosmp' 'nolapic' 'disableapic' */
+	if (!setup_max_cpus || apic_is_disabled)
 		possible = 1;
 
 	/* 'possible_cpus=N' */
@@ -443,7 +443,7 @@ void __init topology_apply_cmdline_limits_early(void)
 
 static __init bool restrict_to_up(void)
 {
-	if (!smp_found_config || ioapic_is_disabled)
+	if (!smp_found_config)
 		return true;
 	/*
 	 * XEN PV is special as it does not advertise the local APIC