linux-kernel - Re: [PATCH 9/9] arm64: Documentation

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Message-ID: <e2f9a241-8453-0b2c-25db-e603b89acf46@reserved-bit.com>
Date:   Wed, 30 Nov 2016 16:44:52 +0530
From:   Siddhesh Poyarekar <sid@...erved-bit.com>
To:     Suzuki K Poulose <suzuki.poulose@....com>,
        linux-arm-kernel@...ts.infradead.org
Cc:     linux-kernel@...r.kernel.org, catalin.marinas@....com,
        dave.martin@....com, aph@...hat.com, will.deacon@....com,
        ryan.arnold@...aro.org, adhemerval.zanella@...aro.org,
        mark.rutland@....com, marc.zyngier@....com
Subject: Re: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers

On Thursday 24 November 2016 07:10 PM, Suzuki K Poulose wrote:
> + d) CPU Identification :
> +    MIDR_EL1 is exposed to help identify the processor. On a
> +    heterogeneous system, this could be racy (just like getcpu()). The
> +    process could be migrated to another CPU by the time it uses the
> +    register value, unless the CPU affinity is set. Hence, there is no
> +    guarantee that the value reflects the processor that it is
> +    currently executing on. The REVIDR is not exposed due to this
> +    constraint, as REVIDR makes sense only in conjunction with the
> +    MIDR. Alternately, MIDR_EL1 and REVIDR_EL1 are exposed via sysfs
> +    at:
> +
> +	/sys/devices/system/cpu/cpu$ID/regs/identification/
> +	                                              \- midr
> +	                                              \- revidr
> +

This doesn't seem to be implemented in this patchset.

Siddhesh