linux-kernel - Re: Early boot regression from f0551af0213 ("x86/topology: Ignore non-present APIC IDs in a present package")

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Date: Thu, 18 Apr 2024 21:13:34 +0200
From: Thomas Gleixner <tglx@...utronix.de>
To: Lyude Paul <lyude@...hat.com>, Borislav Petkov <bp@...en8.de>
Cc: x86@...nel.org, linux-kernel@...r.kernel.org
Subject: Re: Early boot regression from f0551af0213 ("x86/topology: Ignore
 non-present APIC IDs in a present package")

On Thu, Apr 18 2024 at 13:20, Lyude Paul wrote:

> Just gave it a try, unfortunately I'm still seeing the same result on
> that branch.
>
> One more piece of information I apparently missed when reporting this
> yesterday btw: I noticed one more kernel message that comes before the
> panic that's probably relevant:
>
> ..TIMER: vector=0x30 apic1=0 pin1=2 apic2=-1 pin2=-1

Can you please apply the debug patch below which should make it boot
again.

Please also provide the output of the files underneath of

       /sys/kernel/debug/x86/topo/

Thanks,

        tglx
---
 arch/x86/kernel/cpu/topology.c |    7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

--- a/arch/x86/kernel/cpu/topology.c
+++ b/arch/x86/kernel/cpu/topology.c
@@ -176,6 +176,8 @@ static __init void topo_register_apic(u3
 {
 	int cpu, dom;
 
+	pr_info("APIC ID %x present %d\n", apic_id, present);
+
 	if (present) {
 		set_bit(apic_id, phys_cpu_present_map);
 
@@ -201,10 +203,7 @@ static __init void topo_register_apic(u3
 		 */
 		if (hypervisor_is_type(X86_HYPER_NATIVE) &&
 		    topo_unit_count(pkgid, TOPO_PKG_DOMAIN, phys_cpu_present_map)) {
-			pr_info_once("Ignoring hot-pluggable APIC ID %x in present package.\n",
-				     apic_id);
-			topo_info.nr_rejected_cpus++;
-			return;
+			pr_info("Hot-pluggable APIC ID %x in present package.\n", apic_id);
 		}
 
 		topo_info.nr_disabled_cpus++;