linux-kernel - Re: [PATCH v6 02/24] arm64: cpufeature: Set SYSREG_GIC_CPUIF as a boot system feature

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Message-ID: <20181129162722.s2ee2mdteli7jdir@lakrids.cambridge.arm.com>
Date:   Thu, 29 Nov 2018 16:27:22 +0000
From:   Mark Rutland <mark.rutland@....com>
To:     Julien Thierry <julien.thierry@....com>
Cc:     linux-arm-kernel@...ts.infradead.org, daniel.thompson@...aro.org,
        marc.zyngier@....com, catalin.marinas@....com,
        Suzuki K Poulose <suzuki.poulose@....com>,
        will.deacon@....com, linux-kernel@...r.kernel.org,
        christoffer.dall@....com, james.morse@....com,
        joel@...lfernandes.org
Subject: Re: [PATCH v6 02/24] arm64: cpufeature: Set SYSREG_GIC_CPUIF as a
 boot system feature

On Mon, Nov 12, 2018 at 11:56:53AM +0000, Julien Thierry wrote:
> It is not supported to have some CPUs using GICv3 sysreg CPU interface
> while some others do not.
> 
> Once ICC_SRE_EL1.SRE is set on a CPU, the bit cannot be cleared. Since
> matching this feature require setting ICC_SRE_EL1.SRE, it cannot be
> turned off if found on a CPU.
> 
> Set the feature as STRICT_BOOT, if boot CPU has it, all other CPUs are
> required to have it.
> 
> Signed-off-by: Julien Thierry <julien.thierry@....com>
> Suggested-by: Daniel Thompson <daniel.thompson@...aro.org>
> Cc: Catalin Marinas <catalin.marinas@....com>
> Cc: Will Deacon <will.deacon@....com>
> Cc: Suzuki K Poulose <suzuki.poulose@....com>
> Cc: Marc Zyngier <marc.zyngier@....com>

Makes sense.

Reviewed-by: Mark Rutland <mark.rutland@....com>

Mark.

> ---
>  arch/arm64/kernel/cpufeature.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm64/kernel/cpufeature.c b/arch/arm64/kernel/cpufeature.c
> index af50064..03a9d96 100644
> --- a/arch/arm64/kernel/cpufeature.c
> +++ b/arch/arm64/kernel/cpufeature.c
> @@ -1149,7 +1149,7 @@ static void cpu_clear_disr(const struct arm64_cpu_capabilities *__unused)
>  	{
>  		.desc = "GIC system register CPU interface",
>  		.capability = ARM64_HAS_SYSREG_GIC_CPUIF,
> -		.type = ARM64_CPUCAP_SYSTEM_FEATURE,
> +		.type = ARM64_CPUCAP_STRICT_BOOT_CPU_FEATURE,
>  		.matches = has_useable_gicv3_cpuif,
>  		.sys_reg = SYS_ID_AA64PFR0_EL1,
>  		.field_pos = ID_AA64PFR0_GIC_SHIFT,
> -- 
> 1.9.1
> 
> 
> _______________________________________________
> linux-arm-kernel mailing list
> linux-arm-kernel@...ts.infradead.org
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel

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