From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755789AbcK3LcF (ORCPT ); Wed, 30 Nov 2016 06:32:05 -0500 Received: from foss.arm.com ([217.140.101.70]:43462 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754270AbcK3Lbz (ORCPT ); Wed, 30 Nov 2016 06:31:55 -0500 Date: Wed, 30 Nov 2016 11:31:50 +0000 From: Catalin Marinas To: Siddhesh Poyarekar Cc: Suzuki K Poulose , linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, ryan.arnold@linaro.org, aph@redhat.com, will.deacon@arm.com, linux-kernel@vger.kernel.org, marc.zyngier@arm.com, adhemerval.zanella@linaro.org, dave.martin@arm.com Subject: Re: [PATCH 9/9] arm64: Documentation - Expose CPU feature registers Message-ID: <20161130113150.GB4439@e104818-lin.cambridge.arm.com> References: <1479994809-9081-1-git-send-email-suzuki.poulose@arm.com> <1479994809-9081-10-git-send-email-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.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