From mboxrd@z Thu Jan 1 00:00:00 1970 From: catalin.marinas@arm.com (Catalin Marinas) Date: Wed, 30 Nov 2016 11:31:50 +0000 Subject: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers In-Reply-To: References: <1479994809-9081-1-git-send-email-suzuki.poulose@arm.com> <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com> Message-ID: <20161130113150.GB4439@e104818-lin.cambridge.arm.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Wed, Nov 30, 2016 at 04:44:52PM +0530, Siddhesh Poyarekar wrote: > 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. No. However, we merged the functionality above already and forgot about the documentation part, so we just clarify it now. -- Catalin