linux-kernel - [PATCH v2] x86/cpu/topology: remove limit of CPUs due to noapic on x86

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Message-ID: <20241202145243.1228-1-ffmancera@riseup.net>
Date: Mon,  2 Dec 2024 14:52:34 +0000
From: Fernando Fernandez Mancera <ffmancera@...eup.net>
To: linux-kernel@...r.kernel.org
Cc: tglx@...utronix.de,
	x86@...nel.org,
	Fernando Fernandez Mancera <ffmancera@...eup.net>
Subject: [PATCH v2] x86/cpu/topology: remove limit of CPUs due to noapic on x86

On x86 the command line parameter "noapic" should not limit the number
of possible CPUs, as it only limits the use of IRQ sharing or device IRQ
remapping. This restores the behavior previous to the rework of possible
CPUs management.

Fixes: 7c0edad3643f ("x86/cpu/topology: Rework possible CPU management")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@...eup.net>
---
 arch/x86/kernel/cpu/topology.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 621a151ccf7d..b21f28f6a8a8 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' */
@@ -443,8 +443,9 @@ 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
 	 * properly, but provides a fake topology for it so that the
-- 
2.47.1