From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751699AbcGUKPo (ORCPT ); Thu, 21 Jul 2016 06:15:44 -0400 Received: from foss.arm.com ([217.140.101.70]:47134 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751415AbcGUKPl (ORCPT ); Thu, 21 Jul 2016 06:15:41 -0400 From: Suzuki K Poulose To: catalin.marinas@arm.com Cc: will.deacon@arm.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, Suzuki K Poulose , Mark Rutland , James Morse Subject: [PATCH] [4.7] arm64: Honor nosmp kernel command line option Date: Thu, 21 Jul 2016 11:15:27 +0100 Message-Id: <1469096127-1136-1-git-send-email-suzuki.poulose@arm.com> X-Mailer: git-send-email 2.7.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Passing "nosmp" should boot the kernel with a single processor, without provision to enable secondary CPUs even if they are present. "nosmp" is implemented by setting maxcpus=0. At the moment we still mark the secondary CPUs present even with nosmp, which allows the userspace to bring them up. This patch corrects the smp_prepare_cpus() to honor the maxcpus == 0. Commit 44dbcc93ab67145 ("arm64: Fix behavior of maxcpus=N") fixed the behavior for maxcpus >= 1, but broke maxcpus = 0. Fixes: commit 44dbcc93ab67145 ("arm64: Fix behavior of maxcpus=N") Cc: Will Deacon Cc: Catalin Marinas Cc: Mark Rutland Cc: James Morse Signed-off-by: Suzuki K Poulose --- arch/arm64/kernel/smp.c | 7 +++++++ 1 file changed, 7 insertions(+) diff --git a/arch/arm64/kernel/smp.c b/arch/arm64/kernel/smp.c index d242e81..ec08b7a 100644 --- a/arch/arm64/kernel/smp.c +++ b/arch/arm64/kernel/smp.c @@ -694,6 +694,13 @@ void __init smp_prepare_cpus(unsigned int max_cpus) smp_store_cpu_info(smp_processor_id()); /* + * If UP is mandated by "nosmp"(implies maxcpus=0), don't bother about + * secondary CPUs. + */ + if (max_cpus == 0) + return; + + /* * Initialise the present map (which describes the set of CPUs * actually populated at the present time) and release the * secondaries from the bootloader. -- 2.7.4