From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755300AbcK3LkP (ORCPT ); Wed, 30 Nov 2016 06:40:15 -0500 Received: from mx.kolabnow.com ([95.128.36.1]:25788 "EHLO mx-out02.mykolab.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1753383AbcK3LkJ (ORCPT ); Wed, 30 Nov 2016 06:40:09 -0500 X-Spam-Flag: NO X-Spam-Score: -2.9 Subject: Re: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers To: Suzuki K Poulose , linux-arm-kernel@lists.infradead.org References: <1479994809-9081-1-git-send-email-suzuki.poulose@arm.com> <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com> 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 From: Siddhesh Poyarekar Message-ID: Date: Wed, 30 Nov 2016 16:44:52 +0530 MIME-Version: 1.0 In-Reply-To: <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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