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[RFC,v2,31/35] arm64: psci: Ignore DENIED CPUs

Message ID 20230913163823.7880-32-james.morse@arm.com (mailing list archive)
State Handled Elsewhere
Headers show
Series ACPI/arm64: add support for virtual cpuhotplug | expand

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Commit Message

James Morse Sept. 13, 2023, 4:38 p.m. UTC 
From: Jean-Philippe Brucker <jean-philippe@linaro.org>

When a CPU is marked as disabled, but online capable in the MADT, PSCI
applies some firmware policy to control when it can be brought online.
PSCI returns DENIED to a CPU_ON request if this is not currently
permitted. The OS can learn the current policy from the _STA enabled bit.

Handle the PSCI DENIED return code gracefully instead of printing an
error.

Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
[ morse: Rewrote commit message ]
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/psci.c     | 2 +-
 arch/arm64/kernel/smp.c      | 3 ++-
 drivers/firmware/psci/psci.c | 2 ++
 3 files changed, 5 insertions(+), 2 deletions(-)

Comments

Jonathan Cameron Sept. 14, 2023, 4:01 p.m. UTC | #1 
On Wed, 13 Sep 2023 16:38:19 +0000
James Morse <james.morse@arm.com> wrote:

> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
> 
> When a CPU is marked as disabled, but online capable in the MADT, PSCI
> applies some firmware policy to control when it can be brought online.
> PSCI returns DENIED to a CPU_ON request if this is not currently
> permitted. The OS can learn the current policy from the _STA enabled bit.
> 
> Handle the PSCI DENIED return code gracefully instead of printing an
> error.

Specification reference would be good particularly as it's only been
added as a possibility fairly recently.

> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> [ morse: Rewrote commit message ]
> Signed-off-by: James Morse <james.morse@arm.com>
> ---
>  arch/arm64/kernel/psci.c     | 2 +-
>  arch/arm64/kernel/smp.c      | 3 ++-
>  drivers/firmware/psci/psci.c | 2 ++
>  3 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
> index 29a8e444db83..4fcc0cdd757b 100644
> --- a/arch/arm64/kernel/psci.c
> +++ b/arch/arm64/kernel/psci.c
> @@ -40,7 +40,7 @@ static int cpu_psci_cpu_boot(unsigned int cpu)
>  {
>  	phys_addr_t pa_secondary_entry = __pa_symbol(secondary_entry);
>  	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry);
> -	if (err)
> +	if (err && err != -EPROBE_DEFER)

Hmm. EPROBE_DEFER has very specific meaning around driver requesting a retry
when some other bit of the system has finished booting. 
I'm not sure it's a good idea for this use case.  Maybe just keep to EPERM
as psci_to_linux_errno() will return anyway.  Seems valid to me, or
is the requirement to use EPROBE_DEFER coming from further up the stack?



>  		pr_err("failed to boot CPU%d (%d)\n", cpu, err);
>  
>  	return err;
> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
> index 8c8f55721786..e958db987665 100644
> --- a/arch/arm64/kernel/smp.c
> +++ b/arch/arm64/kernel/smp.c
> @@ -124,7 +124,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
>  	/* Now bring the CPU into our world */
>  	ret = boot_secondary(cpu, idle);
>  	if (ret) {
> -		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
> +		if (ret != -EPROBE_DEFER)
> +			pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
>  		return ret;
>  	}
>  
> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
> index d9629ff87861..f7ab3fed3528 100644
> --- a/drivers/firmware/psci/psci.c
> +++ b/drivers/firmware/psci/psci.c
> @@ -218,6 +218,8 @@ static int __psci_cpu_on(u32 fn, unsigned long cpuid, unsigned long entry_point)
>  	int err;
>  
>  	err = invoke_psci_fn(fn, cpuid, entry_point, 0);
> +	if (err == PSCI_RET_DENIED)
> +		return -EPROBE_DEFER;
>  	return psci_to_linux_errno(err);
>  }
>
Gavin Shan Sept. 19, 2023, 4:31 a.m. UTC | #2 
On 9/15/23 02:01, Jonathan Cameron wrote:
> On Wed, 13 Sep 2023 16:38:19 +0000
> James Morse <james.morse@arm.com> wrote:
> 
>> From: Jean-Philippe Brucker <jean-philippe@linaro.org>
>>
>> When a CPU is marked as disabled, but online capable in the MADT, PSCI
>> applies some firmware policy to control when it can be brought online.
>> PSCI returns DENIED to a CPU_ON request if this is not currently
>> permitted. The OS can learn the current policy from the _STA enabled bit.
>>
>> Handle the PSCI DENIED return code gracefully instead of printing an
>> error.
> 
> Specification reference would be good particularly as it's only been
> added as a possibility fairly recently.
> 

https://developer.arm.com/documentation/den0022/f/?lang=en   page-58

It seems DENIED is the best matched indicator.

>>
>> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
>> [ morse: Rewrote commit message ]
>> Signed-off-by: James Morse <james.morse@arm.com>
>> ---
>>   arch/arm64/kernel/psci.c     | 2 +-
>>   arch/arm64/kernel/smp.c      | 3 ++-
>>   drivers/firmware/psci/psci.c | 2 ++
>>   3 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
>> index 29a8e444db83..4fcc0cdd757b 100644
>> --- a/arch/arm64/kernel/psci.c
>> +++ b/arch/arm64/kernel/psci.c
>> @@ -40,7 +40,7 @@ static int cpu_psci_cpu_boot(unsigned int cpu)
>>   {
>>   	phys_addr_t pa_secondary_entry = __pa_symbol(secondary_entry);
>>   	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry);
>> -	if (err)
>> +	if (err && err != -EPROBE_DEFER)
> 
> Hmm. EPROBE_DEFER has very specific meaning around driver requesting a retry
> when some other bit of the system has finished booting.
> I'm not sure it's a good idea for this use case.  Maybe just keep to EPERM
> as psci_to_linux_errno() will return anyway.  Seems valid to me, or
> is the requirement to use EPROBE_DEFER coming from further up the stack?
> 

I agree with Jonathan that -EPERM from psci_to_linux_errno(DENIED) is
good enough here. Actually, I think we need to bail from bringing up
the CPU once error is raised on psci_ops.cpu_on() and avoid reporting
it as error with help of -EPROBE_DEFER. -EPERM can serve the same
purpose.

> 
> 
>>   		pr_err("failed to boot CPU%d (%d)\n", cpu, err);
>>   
>>   	return err;
>> diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
>> index 8c8f55721786..e958db987665 100644
>> --- a/arch/arm64/kernel/smp.c
>> +++ b/arch/arm64/kernel/smp.c
>> @@ -124,7 +124,8 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle)
>>   	/* Now bring the CPU into our world */
>>   	ret = boot_secondary(cpu, idle);
>>   	if (ret) {
>> -		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
>> +		if (ret != -EPROBE_DEFER)
>> +			pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
>>   		return ret;
>>   	}
>>   
>> diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
>> index d9629ff87861..f7ab3fed3528 100644
>> --- a/drivers/firmware/psci/psci.c
>> +++ b/drivers/firmware/psci/psci.c
>> @@ -218,6 +218,8 @@ static int __psci_cpu_on(u32 fn, unsigned long cpuid, unsigned long entry_point)
>>   	int err;
>>   
>>   	err = invoke_psci_fn(fn, cpuid, entry_point, 0);
>> +	if (err == PSCI_RET_DENIED)
>> +		return -EPROBE_DEFER;
>>   	return psci_to_linux_errno(err);
>>   }
>>   

Thanks,
Gavin
diff mbox series

Patch

diff --git a/arch/arm64/kernel/psci.c b/arch/arm64/kernel/psci.c
index 29a8e444db83..4fcc0cdd757b 100644
--- a/arch/arm64/kernel/psci.c
+++ b/arch/arm64/kernel/psci.c
@@ -40,7 +40,7 @@  static int cpu_psci_cpu_boot(unsigned int cpu)
 {
 	phys_addr_t pa_secondary_entry = __pa_symbol(secondary_entry);
 	int err = psci_ops.cpu_on(cpu_logical_map(cpu), pa_secondary_entry);
-	if (err)
+	if (err && err != -EPROBE_DEFER)
 		pr_err("failed to boot CPU%d (%d)\n", cpu, err);
 
 	return err;
diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c
index 8c8f55721786..e958db987665 100644
--- a/arch/arm64/kernel/smp.c
+++ b/arch/arm64/kernel/smp.c
@@ -124,7 +124,8 @@  int __cpu_up(unsigned int cpu, struct task_struct *idle)
 	/* Now bring the CPU into our world */
 	ret = boot_secondary(cpu, idle);
 	if (ret) {
-		pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
+		if (ret != -EPROBE_DEFER)
+			pr_err("CPU%u: failed to boot: %d\n", cpu, ret);
 		return ret;
 	}
 
diff --git a/drivers/firmware/psci/psci.c b/drivers/firmware/psci/psci.c
index d9629ff87861..f7ab3fed3528 100644
--- a/drivers/firmware/psci/psci.c
+++ b/drivers/firmware/psci/psci.c
@@ -218,6 +218,8 @@  static int __psci_cpu_on(u32 fn, unsigned long cpuid, unsigned long entry_point)
 	int err;
 
 	err = invoke_psci_fn(fn, cpuid, entry_point, 0);
+	if (err == PSCI_RET_DENIED)
+		return -EPROBE_DEFER;
 	return psci_to_linux_errno(err);
 }