From mboxrd@z Thu Jan 1 00:00:00 1970 From: sid@reserved-bit.com (Siddhesh Poyarekar) Date: Wed, 30 Nov 2016 16:44:52 +0530 Subject: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers In-Reply-To: <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com> References: <1479994809-9081-1-git-send-email-suzuki.poulose@arm.com> <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com> Message-ID: To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org 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