From patchwork Wed Jul 8 10:58:47 2015 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Catalin Marinas X-Patchwork-Id: 6744741 Return-Path: X-Original-To: patchwork-linux-arm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id A1CD09F319 for ; Wed, 8 Jul 2015 11:01:34 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id C57FE206E9 for ; Wed, 8 Jul 2015 11:01:33 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.9]) (using TLSv1.2 with cipher AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 97A95206DD for ; Wed, 8 Jul 2015 11:01:31 +0000 (UTC) Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZCn4O-0003ao-Tq; Wed, 08 Jul 2015 10:59:16 +0000 Received: from foss.arm.com ([217.140.101.70]) by bombadil.infradead.org with esmtp (Exim 4.80.1 #2 (Red Hat Linux)) id 1ZCn4M-0003Vp-BN for linux-arm-kernel@lists.infradead.org; Wed, 08 Jul 2015 10:59:14 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E2D8D317; Wed, 8 Jul 2015 03:59:16 -0700 (PDT) Received: from e104818-lin.cambridge.arm.com (usa-sjc-imap-foss1.foss.arm.com [10.72.51.249]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 1FDB83F581; Wed, 8 Jul 2015 03:58:49 -0700 (PDT) Date: Wed, 8 Jul 2015 11:58:47 +0100 From: Catalin Marinas To: Will Deacon Subject: Re: [RFC PATCH] arm64: force CONFIG_SMP=y and remove redundant #ifdefs Message-ID: <20150708105847.GB6944@e104818-lin.cambridge.arm.com> References: <1436293575-5101-1-git-send-email-will.deacon@arm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1436293575-5101-1-git-send-email-will.deacon@arm.com> User-Agent: Mutt/1.5.23 (2014-03-12) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20150708_035914_395640_3CF6F90B X-CRM114-Status: GOOD ( 15.65 ) X-Spam-Score: -7.7 (-------) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.20 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org X-Spam-Status: No, score=-4.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_MED, RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Tue, Jul 07, 2015 at 07:26:15PM +0100, Will Deacon wrote: > Nobody seems to be producing !SMP systems anymore, so this is just > becoming a source of kernel bugs, particularly if people want to use > coherent DMA with non-shared pages. > > This patch forces CONFIG_SMP=y for arm64, removing a modest amount of > code in the process. > > Signed-off-by: Will Deacon > --- > > I'd appreciate any comments on this. Anybody got a good reason for > CONFIG_SMP=n on arm64? A good reason would be testing/validating some hardware configurations or even KVM/Xen (to see how they cope with UP OS'es). Of course, this still requires that someone tests UP builds regularly but at least under KVM this shouldn't be hard. An alternative, which does not remove any code: The help text needs re-writing as well, it doesn't make much sense these days. diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 318175f62c24..8610effa5b0d 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -475,7 +475,8 @@ config CPU_BIG_ENDIAN Say Y if you plan on running a kernel in big-endian mode. config SMP - bool "Symmetric Multi-Processing" + bool "Symmetric Multi-Processing" if EXPERT + default y help This enables support for systems with more than one CPU. If you say N here, the kernel will run on single and