From: Siddhesh Poyarekar <sid@reserved-bit.com>
To: Suzuki K Poulose <suzuki.poulose@arm.com>,
linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com,
dave.martin@arm.com, aph@redhat.com, will.deacon@arm.com,
ryan.arnold@linaro.org, adhemerval.zanella@linaro.org,
mark.rutland@arm.com, marc.zyngier@arm.com
Subject: Re: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers
Date: Wed, 30 Nov 2016 16:44:52 +0530 [thread overview]
Message-ID: <e2f9a241-8453-0b2c-25db-e603b89acf46@reserved-bit.com> (raw)
In-Reply-To: <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com>
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
next prev parent reply other threads:[~2016-11-30 11:40 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-11-24 13:40 [PATCH 0/9] arm64: Expose CPUID registers via emulation Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 1/9] arm64: cpufeature: treat unknown fields as RES0 Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 2/9] arm64: cpufeature: remove explicit RAZ fields Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 3/9] arm64: cpufeature: Cleanup feature bit tables Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 4/9] arm64: cpufeature: Document the rules of safe value for features Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 5/9] arm64: cpufeature: Define helpers for sys_reg id Suzuki K Poulose
2016-11-30 11:04 ` Will Deacon
2016-11-30 14:16 ` Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 6/9] arm64: Add helper to decode register from instruction Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 7/9] arm64: cpufeature: Track user visible fields Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 8/9] arm64: cpufeature: Expose CPUID registers by emulation Suzuki K Poulose
2016-11-24 13:40 ` [PATCH 9/9] arm64: Documentation - Expose CPU feature registers Suzuki K Poulose
2016-11-24 18:44 ` Catalin Marinas
2016-11-30 11:41 ` Suzuki K Poulose
2016-11-30 11:14 ` Siddhesh Poyarekar [this message]
2016-11-30 11:30 ` Suzuki K Poulose
2016-11-30 11:33 ` Siddhesh Poyarekar
2016-11-30 11:31 ` Catalin Marinas
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