Re: [PATCH v8 12/16] arm64: psci: Ignore DENIED CPUs

[Gavin Shan <gshan@redhat.com>]

On 4/26/24 23:51, Jonathan Cameron 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.
> 
> Note the alternatives to the PSCI cpu_boot() callback do not
> return -EPERM so the change in smp.c has no affect.
> 
> See https://developer.arm.com/documentation/den0022/f/?lang=en page 58.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@linaro.org>
> [ morse: Rewrote commit message ]
> Signed-off-by: James Morse <james.morse@arm.com>
> Tested-by: Miguel Luis <miguel.luis@oracle.com>
> Tested-by: Vishnu Pajjuri <vishnu@os.amperecomputing.com>
> Tested-by: Jianyong Wu <jianyong.wu@arm.com>
> Reviewed-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@armlinux.org.uk>
> Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
> ---
> v8: Note in commit message that the -EPERM guard on the error print
>      only affects PSCI as other options never use this error code.
>      Should they do so in future, that may well indicate that they
>      now support similar refusal to boot.
> ---
>   arch/arm64/kernel/psci.c | 2 +-
>   arch/arm64/kernel/smp.c  | 3 ++-
>   2 files changed, 3 insertions(+), 2 deletions(-)
> 

Thanks for the check and clarification that -EPERM is only sensible
to PSCI. With the clarification:

Reviewed-by: Gavin Shan <gshan@redhat.com>

Thanks,
Gavin