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@riseup.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20241202145905.1482-1-ffmancera@riseup.net

diff --git a/arch/x86/kernel/cpu/topology.c b/arch/x86/kernel/cpu/topology.c
index 621a151ccf7d0a89699a9db2bd619b4fa92bfd47..b2e313ea17bf6f590029ccfea26af52c7f82967d 100644 (file)
--- 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