From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752321AbcDZOut (ORCPT ); Tue, 26 Apr 2016 10:50:49 -0400 Received: from foss.arm.com ([217.140.101.70]:55157 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751829AbcDZOus (ORCPT ); Tue, 26 Apr 2016 10:50:48 -0400 Date: Tue, 26 Apr 2016 15:50:46 +0100 From: Will Deacon To: Suzuki K Poulose Cc: linux-arm-kernel@lists.infradead.org, mark.rutland@arm.com, marc.zyngier@arm.com, linux-kernel@vger.kernel.org, catalin.marinas@arm.com, Vadim.Lomovtsev@caviumnetworks.com Subject: Re: [PATCH v5 0/5] arm64: Fix behavior of maxcpus=n Message-ID: <20160426145046.GB1793@arm.com> References: <1461682140-7131-1-git-send-email-suzuki.poulose@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1461682140-7131-1-git-send-email-suzuki.poulose@arm.com> 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 Tue, Apr 26, 2016 at 03:48:55PM +0100, Suzuki K Poulose wrote: > This series is an attempt at fixing the maxcpus=n behavior > on arm64. So far we have disabled hotplugging a CPU > n, > when maxcpus=n is in effect, due to following reasons. > > 1) Possible cpu feature incompatibilities with the new CPU > in heterogeneous systems. > 2) New CPU requiring an errata work around which was not detected > (and the code patched in) at boot time. > 3) Failure to initialise the PMU in case the supported CPUs are > not online while probing the PMU. > > (1) has been mostly solved with our early CPU feature verification > support. This series tries to address (2) & (3). > > (2) is solved by iterating over the known erratas and checking if > the new CPU requires an errata not set in the cpu_hwcaps, failing > which, we kill the CPU. We plan to fix this properly by retaining > the CPU errata work arounds and apply the required at runtime. > > (3) is ignored and will not be fixed as there is no reliable way of > knowing if there would be a CPU that will be online to support the > PMU. > > In the process, also restores the capability to check GIC interface settings > by the firmware on individual CPUs. > > Tested on Juno with maxcpus=2 (enables A57 cores and A57-PMU) and > maxcpus=1 (disables both A57 cores and A57-PMU). > > This series applies on aarch64/for-next/core : > > The tree is available here : > git://linux-arm.org/linux-skp.git maxcpus/v5 > > Changes since V4: > - Address Catalin's comments > - Rebased to aarch64 for-next/core > - Add Reviewed/Acked bys. I merged this yesterday onto for-next/core. Please can you check that I fixed everything up that you expected? Will