Bogus "APIC: NR_CPUS/possible_cpus limit of 4 reached" messages

DISCUSSION Markus Trippelsdorf 4 participants 7 messages Oct 6, 2016 – Oct 8, 2016

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x86 ACPI

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Markus Trippelsdorf

author

2016-10-06 11:27 UTC #0 lore raw

On current trunk I get during boot:

[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 4/0x84 ignored.
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 5/0x85 ignored.

I don't think these messages make much sense on a 4-core machine.

Signature · 1 line

Markus

One Thousand Gnomes

2016-10-06 11:48 UTC #1 lore raw

Quoted 7 lines · On Thu, 6 Oct 2016 13:27:37 +0200 Markus Trippelsdorf <[email protected]>…

On current trunk I get during boot:
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 4/0x84 ignored.
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 5/0x85 ignored.
I don't think these messages make much sense on a 4-core machine.

Four cores with or without hyperthreading ?

Alan

Markus Trippelsdorf

author

2016-10-06 11:52 UTC #2 lore raw

Quoted 5 lines · One Thousand Gnomes

Quoted 2 lines · On Thu, 6 Oct 2016 13:27:37 +0200 Markus Trippelsdorf <[email protected]>…
On current trunk I get during boot:

Quoted 7 lines

Quoted 5 lines
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 4/0x84 ignored.
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 5/0x85 ignored.
I don't think these messages make much sense on a 4-core machine.
Four cores with or without hyperthreading ?

Without. This is a rather old AMD machine (AMD Phenom II X4 955).

Signature · 1 line

Markus

Markus Trippelsdorf

author

2016-10-07 13:26 UTC #3 lore raw

Quoted 9 lines · Markus Trippelsdorf

Quoted 8 lines · One Thousand Gnomes
Quoted 5 lines · On Thu, 6 Oct 2016 13:27:37 +0200 Markus Trippelsdorf <[email protected]>…
On current trunk I get during boot:
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 4/0x84 ignored.
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 5/0x85 ignored.

Quoted 6 lines

Quoted 4 lines
Quoted 2 lines
I don't think these messages make much sense on a 4-core machine.
Four cores with or without hyperthreading ?
Without. This is a rather old AMD machine (AMD Phenom II X4 955).

CCing more people.

Signature · 1 line

Markus

Thomas Gleixner

2016-10-07 13:58 UTC #4 lore raw

Quoted 10 lines · Markus Trippelsdorf

Quoted 9 lines · Markus Trippelsdorf
Quoted 8 lines · One Thousand Gnomes
Quoted 5 lines · On Thu, 6 Oct 2016 13:27:37 +0200 Markus Trippelsdorf <[email protected]>…
On current trunk I get during boot:
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 4/0x84 ignored.
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 5/0x85 ignored.

Quoted 6 lines

Quoted 6 lines
Quoted 4 lines
Quoted 2 lines
I don't think these messages make much sense on a 4-core machine.
Four cores with or without hyperthreading ?
Without. This is a rather old AMD machine (AMD Phenom II X4 955).

That's due to the recent cpuid -> nodeid changes. The patch below should fix it.

Thanks,

tglx

arch/x86/kernel/apic/apic.c +5 -3

index f266b8a92a9e..88c657b057e2 100644
@@ -2128,9 +2128,11 @@ int __generic_processor_info(int apicid, int version, bool enabled)
 	if (num_processors >= nr_cpu_ids) {
 		int thiscpu = max + disabled_cpus;
 
-		pr_warning(
-			"APIC: NR_CPUS/possible_cpus limit of %i reached."
-			"  Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
+		if (enabled) {
+			pr_warning("APIC: NR_CPUS/possible_cpus limit of %i "
+				   "reached. Processor %d/0x%x ignored.\n",
+				   max, thiscpu, apicid);
+		}
 
 		disabled_cpus++;
 		return -EINVAL;

Markus Trippelsdorf

author

2016-10-07 14:09 UTC #5 lore raw

Quoted 14 lines · Thomas Gleixner

Quoted 13 lines · Markus Trippelsdorf
Quoted 12 lines · Markus Trippelsdorf
Quoted 11 lines · One Thousand Gnomes
Quoted 7 lines · On Thu, 6 Oct 2016 13:27:37 +0200 Markus Trippelsdorf <[email protected]>…
On current trunk I get during boot:
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 4/0x84 ignored.
[    0.000000] APIC: NR_CPUS/possible_cpus limit of 4 reached.  Processor 5/0x85 ignored.
I don't think these messages make much sense on a 4-core machine.

Quoted 6 lines

Quoted 3 lines
Quoted 3 lines
Quoted 1 line
Four cores with or without hyperthreading ?
Without. This is a rather old AMD machine (AMD Phenom II X4 955).
That's due to the recent cpuid -> nodeid changes. The patch below should fix it.

Indeed it does. Thanks for the quick fix.

Signature · 1 line

Markus

tip-bot for Thomas Gleixner

merge bot

2016-10-08 10:25 UTC #6 lore raw

[tip:x86/urgent] x86/apic: Prevent pointless warning messages

In reply to Thomas Gleixner

x86/apic: Prevent pointless warning messages

Commit-ID:  df610d678893c85b82d3a68eea0d87dd4e03e615
Gitweb:     http://git.kernel.org/tip/df610d678893c85b82d3a68eea0d87dd4e03e615
Author:     Thomas Gleixner <[email protected]>
AuthorDate: Fri, 7 Oct 2016 15:55:13 +0200
Committer:  Thomas Gleixner <[email protected]>
CommitDate: Sat, 8 Oct 2016 12:18:36 +0200

x86/apic: Prevent pointless warning messages

Markus reported that he sees new warnings:

APIC: NR_CPUS/possible_cpus limit of 4 reached. Processor 4/0x84 ignored.
APIC: NR_CPUS/possible_cpus limit of 4 reached. Processor 5/0x85 ignored.

This comes from the recent persistant cpuid - nodeid changes. The code which emits the warning has been called prior to these changes only for enabled processors. Now it's called for disabled processors as well to get the possible cpu accounting correct. So if the kernel is compiled for the number of actual available/enabled CPUs and the BIOS reports disabled CPUs as well then the above warnings are printed.

That's a pointless exercise as it only makes sense if there are more CPUs enabled than the kernel supports.

Nake the warning conditional on enabled processors so we are back to the state before these changes.

Fixes 8f54969dc8d6 ("x86/acpi: Introduce persistent storage for cpuid <-> apicid mapping")

Reported-and-tested-by Markus Trippelsdorf <[email protected]>

Cc One Thousand Gnomes <[email protected]>

Cc Dou Liyang <[email protected]>

Cc [email protected]

Cc Gu Zheng <[email protected]>

Link http://lkml.kernel.org/r/alpine.DEB.2.20.1610071549330.19804@nanos open here

Signed-off-by Thomas Gleixner <[email protected]>

---
 arch/x86/kernel/apic/apic.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

arch/x86/kernel/apic/apic.c +5 -3

index f266b8a..88c657b 100644
@@ -2128,9 +2128,11 @@ int __generic_processor_info(int apicid, int version, bool enabled)
 	if (num_processors >= nr_cpu_ids) {
 		int thiscpu = max + disabled_cpus;
 
-		pr_warning(
-			"APIC: NR_CPUS/possible_cpus limit of %i reached."
-			"  Processor %d/0x%x ignored.\n", max, thiscpu, apicid);
+		if (enabled) {
+			pr_warning("APIC: NR_CPUS/possible_cpus limit of %i "
+				   "reached. Processor %d/0x%x ignored.\n",
+				   max, thiscpu, apicid);
+		}
 
 		disabled_cpus++;
 		return -EINVAL;