ARM64 / SMP: Switch pr_err() to pr_debug() for disabled GICC entry

PATCH Superseded Hanjun Guo 5 participants 7 messages Jul 1, 2015 – Jul 3, 2015

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Hanjun Guo

author

2015-07-01 13:37 UTC #0 lore raw

PATCH 1/1 ARM64 / SMP: Switch pr_err() to pr_debug() for disabled GICC entry

It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.

Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.

So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.

Signed-off-by Hanjun Guo <[email protected]>

---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

arch/arm64/kernel/smp.c +1 -1

index 4b2121b..5caf04a 100644
@@ -402,7 +402,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 	}
 
 	if (!(processor->flags & ACPI_MADT_ENABLED)) {
-		pr_err("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
+		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
 		return;
 	}

Signature · 1 line

1.9.1

Al Stone

Reviewed-by on v1 1/1

2015-07-01 17:02 UTC #1 lore raw

Quoted 23 lines · Hanjun Guo

It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.
Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.
So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.
Signed-off-by Hanjun Guo <[email protected]>
---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/arm64/kernel/smp.c +0 -0
index 4b2121b..5caf04a 100644

arch/arm64/kernel/smp.c acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor) · line 408

Quoted 8 lines

arch/arm64/kernel/smp.c +1 -1

@@ -402,7 +402,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 	}
 
 	if (!(processor->flags & ACPI_MADT_ENABLED)) {
-		pr_err("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
+		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
 		return;
 	}

Yeah, good point. I'm all for making the boot a little quieter by default.

Reviewed-by Al Stone <[email protected]>

Signature · 8 lines

ciao,
al
-----------------------------------
Al Stone
Software Engineer
Red Hat, Inc.
ahs3 at redhat.com
-----------------------------------

Catalin Marinas

maintainer

2015-07-02 16:29 UTC #2 lore raw

In reply to Hanjun Guo

Quoted 22 lines · Hanjun Guo

It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.
Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.
So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.
Signed-off-by Hanjun Guo <[email protected]>
---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/arm64/kernel/smp.c +0 -0
index 4b2121b..5caf04a 100644

arch/arm64/kernel/smp.c acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor) · line 405

Quoted 5 lines

arch/arm64/kernel/smp.c +1 -1

@@ -402,7 +402,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 	}
 
 	if (!(processor->flags & ACPI_MADT_ENABLED)) {
-		pr_err("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
+		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);

That's a pretty harmless change. But looking at the use-case, would we expect the disabled entries to have a valid hwid? I guess such hwid is not known, especially if we can hot-plug some CPU at a later time. If that's the case, can we also move this check before the hwid one?

Signature · 1 line

Catalin

Mark Salter

2015-07-02 17:40 UTC #3 lore raw

Quoted 26 lines · Catalin Marinas

Quoted 24 lines · Hanjun Guo
It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.
Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.
So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.
Signed-off-by Hanjun Guo <[email protected]>
---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/arm64/kernel/smp.c +0 -0
index 4b2121b..5caf04a 100644
@@ -402,7 +402,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 	}
 

Quoted 9 lines

arch/arm64/kernel/smp.c acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor) · line 405
Quoted 3 lines
arch/arm64/kernel/smp.c +1 -1
 	if (!(processor->flags & ACPI_MADT_ENABLED)) {
-		pr_err("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
+		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
That's a pretty harmless change. But looking at the use-case, would we expect the disabled entries to have a valid hwid? I guess such hwid is not known, especially if we can hot-plug some CPU at a later time. If that's the case, can we also move this check before the hwid one?

Heh, I should have read ahead. I just made the same point in a mail I just sent.

Hanjun Guo

2015-07-03 01:15 UTC #4 lore raw

PATCH 1/1 ARM64 / SMP: Switch pr_err() to pr_debug() for disabled GICC entry

In reply to Catalin Marinas

Quoted 25 lines · Catalin Marinas

Quoted 24 lines · Hanjun Guo
It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.
Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.
So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.
Signed-off-by Hanjun Guo <[email protected]>
---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
arch/arm64/kernel/smp.c +0 -0
index 4b2121b..5caf04a 100644
@@ -402,7 +402,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 	}
 

Quoted 6 lines

arch/arm64/kernel/smp.c acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor) · line 405
Quoted 3 lines
arch/arm64/kernel/smp.c +1 -1
 	if (!(processor->flags & ACPI_MADT_ENABLED)) {
-		pr_err("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
+		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
That's a pretty harmless change. But looking at the use-case, would we expect the disabled entries to have a valid hwid? I guess such hwid is not known, especially if we can hot-plug some CPU at a later time. If

Good point, usually it's invalid hwid.

Quoted 1 line

that's the case, can we also move this check before the hwid one?

Yes, fully agree, thanks for catching this, will update the patch.

Thanks
Hanjun

Mark Salter

2015-07-02 17:38 UTC #5 lore raw

In reply to Hanjun Guo

Quoted 5 lines · Hanjun Guo

It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.

Quoted 7 lines

Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.
So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.

I agree with pr_debug instead of pr_err, but for hotplug to work I think we need to continue to parse the MADT instead of bailing out altogether, right? We need to know at init time how many possible cpus there are and that number never changes as cpus are plugged/unplugged. Right now, set_cpu_possible() only gets called if smp_cpu_setup() gets called and smp_cpu_setup() only gets called if the cpu is in the cpu_logical_map.

Quoted 18 lines

Signed-off-by Hanjun Guo <[email protected]>

---
 arch/arm64/kernel/smp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

arch/arm64/kernel/smp.c +1 -1

index 4b2121b..5caf04a 100644
@@ -402,7 +402,7 @@ acpi_map_gic_cpu_interface(struct acpi_madt_generic_interrupt *processor)
 	}
 
 	if (!(processor->flags & ACPI_MADT_ENABLED)) {
-		pr_err("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
+		pr_debug("skipping disabled CPU entry with 0x%llx MPIDR\n", hwid);
 		return;
 	}

Hanjun Guo

2015-07-03 01:18 UTC #6 lore raw

Quoted 11 lines · Mark Salter

Quoted 9 lines · Hanjun Guo
It is normal that firmware presents GICC entry or entries (processors) with disabled flag in ACPI MADT, taking a system of 16 cpus for example, ACPI firmware may present 8 enabled first with another 8 cpus disabled in MADT, the disabled cpus can be hot-added later.
Firmware may also present more cpus than the hardware actually has, but disabled the unused ones, and easily enable it when the hardware has such cpus to make the firmware code scalable.

Quoted 6 lines

Quoted 3 lines
So that's not an error for disabled cpus in MADT, we can switch pr_err() to pr_debug() instead.
I agree with pr_debug instead of pr_err, but for hotplug to work I think we need to continue to parse the MADT instead of bailing out altogether, right? We need to know at init time how many

Yes, agreed :)

Quoted 4 lines

possible cpus there are and that number never changes as cpus are plugged/unplugged. Right now, set_cpu_possible() only gets called if smp_cpu_setup() gets called and smp_cpu_setup() only gets called if the cpu is in the cpu_logical_map.

We need some extra work to make the physical CPU hotplug work on ARM64.

Thanks
Hanjun