linux-kernel - RE: [PATCH 34/39] arm64: psci: Ignore DENIED CPUs

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Date:   Thu, 16 Nov 2023 07:45:51 +0000
From:   Jianyong Wu <Jianyong.Wu@....com>
To:     Russell King <rmk+kernel@...linux.org.uk>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        "loongarch@...ts.linux.dev" <loongarch@...ts.linux.dev>,
        "linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
        "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
        "kvmarm@...ts.linux.dev" <kvmarm@...ts.linux.dev>,
        "x86@...nel.org" <x86@...nel.org>,
        "linux-csky@...r.kernel.org" <linux-csky@...r.kernel.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-ia64@...r.kernel.org" <linux-ia64@...r.kernel.org>,
        "linux-parisc@...r.kernel.org" <linux-parisc@...r.kernel.org>
CC:     Salil Mehta <salil.mehta@...wei.com>,
        Jean-Philippe Brucker <jean-philippe@...aro.org>,
        Justin He <Justin.He@....com>,
        James Morse <James.Morse@....com>,
        Catalin Marinas <Catalin.Marinas@....com>,
        Will Deacon <will@...nel.org>,
        Mark Rutland <Mark.Rutland@....com>,
        Lorenzo Pieralisi <lpieralisi@...nel.org>
Subject: RE: [PATCH 34/39] arm64: psci: Ignore DENIED CPUs

Hi Russell,

One inline comment.

> -----Original Message-----
> From: Russell King <rmk@...linux.org.uk> On Behalf Of Russell King
> Sent: 2023年10月24日 23:19
> To: linux-pm@...r.kernel.org; loongarch@...ts.linux.dev;
> linux-acpi@...r.kernel.org; linux-arch@...r.kernel.org;
> linux-kernel@...r.kernel.org; linux-arm-kernel@...ts.infradead.org;
> linux-riscv@...ts.infradead.org; kvmarm@...ts.linux.dev; x86@...nel.org;
> linux-csky@...r.kernel.org; linux-doc@...r.kernel.org;
> linux-ia64@...r.kernel.org; linux-parisc@...r.kernel.org
> Cc: Salil Mehta <salil.mehta@...wei.com>; Jean-Philippe Brucker
> <jean-philippe@...aro.org>; Jianyong Wu <Jianyong.Wu@....com>; Justin He
> <Justin.He@....com>; James Morse <James.Morse@....com>; Catalin
> Marinas <Catalin.Marinas@....com>; Will Deacon <will@...nel.org>; Mark
> Rutland <Mark.Rutland@....com>; Lorenzo Pieralisi <lpieralisi@...nel.org>
> Subject: [PATCH 34/39] arm64: psci: Ignore DENIED CPUs
> 
> From: Jean-Philippe Brucker <jean-philippe@...aro.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.
> 
> See https://developer.arm.com/documentation/den0022/f/?lang=en page 58.
> 
> Signed-off-by: Jean-Philippe Brucker <jean-philippe@...aro.org> [ morse:
> Rewrote commit message ]
> Signed-off-by: James Morse <james.morse@....com>
> Signed-off-by: Russell King (Oracle) <rmk+kernel@...linux.org.uk>
> ---
> Changes since RFC v2
>  * Add specification reference
>  * Use EPERM rather than EPROBE_DEFER
> ---
>  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)

Should this be EPERM? As the following psci cpu_on op will return it. I think you miss to change this when apply Jean-Philippe's patch.

Thanks
Jianyong
>  		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..68ec7fbe166f 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 != -EPERM)
> +			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..ee82e7880d8c 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 -EPERM;
>  	return psci_to_linux_errno(err);
>  }
> 
> --
> 2.30.2