From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-16.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 13979C433EF for ; Wed, 8 Sep 2021 07:45:39 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8A4F361168 for ; Wed, 8 Sep 2021 07:45:38 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org 8A4F361168 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=kvack.org Received: by kanga.kvack.org (Postfix) id 9FD5B6B006C; Wed, 8 Sep 2021 03:45:37 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 985FB6B0071; Wed, 8 Sep 2021 03:45:37 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8277B6B0072; Wed, 8 Sep 2021 03:45:37 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0045.hostedemail.com [216.40.44.45]) by kanga.kvack.org (Postfix) with ESMTP id 6EB5D6B006C for ; Wed, 8 Sep 2021 03:45:37 -0400 (EDT) Received: from smtpin33.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id F07F21815EB48 for ; Wed, 8 Sep 2021 07:45:36 +0000 (UTC) X-FDA: 78563621472.33.E545E5B Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by imf10.hostedemail.com (Postfix) with ESMTP id 938B56001984 for ; Wed, 8 Sep 2021 07:45:36 +0000 (UTC) Received: by mail.kernel.org (Postfix) with ESMTPSA id A898161168 for ; Wed, 8 Sep 2021 07:45:35 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1631087135; bh=PoRu+CAUg3VBGh79YA9R6PzT7K6KJSWvOcZiEPGVbg4=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=hwdvwbkgODALuKqNxKonrXkN90p2soca7NQhu65Y+1qOx3s0t7h4goIMJ6sOv87Zs azNOOjusDsVEUvUV5Vvw40ZO5EJzRsC8RlDtREHOkZJhXAwTIGTsEIR1HIFSPnAIOk qL5+ObCrLt/0YPTqhoHjMkCZoAl340mJ7WJfIArRSH8I3mi7i5hcFE9bVMjSijyCPn 5/FueRobVSj11GcqGxjTold3u/G8ijrMA0jzwS+zkZNk8Du6fFun2uhcMAQxbMMQzr lyQgpg6bzBL875p8o0UhYDkO0Bj/Of9pdxbif59psmtrbLCVjnA7EOZTfPmUDHKgiU znPksNp8TNIbA== Received: by mail-ot1-f44.google.com with SMTP id v33-20020a0568300921b0290517cd06302dso1796723ott.13 for ; Wed, 08 Sep 2021 00:45:35 -0700 (PDT) X-Gm-Message-State: AOAM532bUQtIDCWFq862hySjvCcxGK3XozKLVWDZnY5UWkpwdygqPjyg TrpAL4a4m9zemDeFPzRoCBpn5bPEfGUOncEZpY0= X-Google-Smtp-Source: ABdhPJyOB6Ole19/mwc56/w3p7NNTf7L8aSx0sEgGjXiC1beNoWvMENfg8b+dzFoh7My+WOm51sTIvD4nhu65WLM/N4= X-Received: by 2002:a9d:12e2:: with SMTP id g89mr2050992otg.112.1631087135031; Wed, 08 Sep 2021 00:45:35 -0700 (PDT) MIME-Version: 1.0 References: <20210904060908.1310204-1-keithp@keithp.com> <20210907220038.91021-1-keithpac@amazon.com> <20210907220038.91021-5-keithpac@amazon.com> In-Reply-To: <20210907220038.91021-5-keithpac@amazon.com> From: Ard Biesheuvel Date: Wed, 8 Sep 2021 09:45:23 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 4/7] ARM: Use hack from powerpc to get current cpu number To: Keith Packard Cc: Linux Kernel Mailing List , Abbott Liu , Andrew Morton , Andrey Ryabinin , Anshuman Khandual , Arnd Bergmann , Bjorn Andersson , Christoph Lameter , Dennis Zhou , Geert Uytterhoeven , Jens Axboe , Joe Perches , Kees Cook , Krzysztof Kozlowski , Linus Walleij , Linux ARM , Linux Memory Management List , Manivannan Sadhasivam , Marc Zyngier , Masahiro Yamada , Mike Rapoport , Nathan Chancellor , Nick Desaulniers , Nick Desaulniers , Nicolas Pitre , Russell King , Tejun Heo , Thomas Gleixner , =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= , Valentin Schneider , Viresh Kumar , "Wolfram Sang (Renesas)" , YiFei Zhu Content-Type: text/plain; charset="UTF-8" Authentication-Results: imf10.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=hwdvwbkg; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf10.hostedemail.com: domain of ardb@kernel.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=ardb@kernel.org X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 938B56001984 X-Stat-Signature: gyxownwm746doj5ctd116bh3119g5yd7 X-HE-Tag: 1631087136-637980 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Wed, 8 Sept 2021 at 00:00, Keith Packard wrote: > > When we enable THREAD_INFO_IN_TASK, the cpu number will disappear from > thread_info and reappear in task_struct. As we cannot include > linux/sched.h in asm/smp.h, there's no way to use that struct type in > the raw_smp_processor_id macro. Instead, a hack from the powerpc code > is used. This pulls the TI_CPU offset out of asm-offsets.h and uses > that to find the cpu value. > > Signed-off-by: Keith Packard > --- > arch/arm/Makefile | 8 ++++++++ > arch/arm/include/asm/smp.h | 18 +++++++++++++++++- > 2 files changed, 25 insertions(+), 1 deletion(-) > > diff --git a/arch/arm/Makefile b/arch/arm/Makefile > index 415c3514573a..6752995d2914 100644 > --- a/arch/arm/Makefile > +++ b/arch/arm/Makefile > @@ -284,6 +284,14 @@ stack_protector_prepare: prepare0 > $(eval GCC_PLUGINS_CFLAGS += $(SSP_PLUGIN_CFLAGS)) > endif > > +ifdef CONFIG_SMP > +prepare: task_cpu_prepare > + > +PHONY += task_cpu_prepare > +task_cpu_prepare: prepare0 > + $(eval KBUILD_CFLAGS += -D_TI_CPU=$(shell awk '{if ($$2 == "TI_CPU") print $$3;}' include/generated/asm-offsets.h)) > +endif > + > all: $(notdir $(KBUILD_IMAGE)) > > > diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h > index d43b64635d77..f77ba3753bc4 100644 > --- a/arch/arm/include/asm/smp.h > +++ b/arch/arm/include/asm/smp.h > @@ -15,7 +15,23 @@ > # error " included in non-SMP build" > #endif > > -#define raw_smp_processor_id() (current_thread_info()->cpu) > +/* > + * This is particularly ugly: it appears we can't actually get the > + * definition of task_struct here, but we need access to the CPU this > + * task is running on, which is stored in task_struct when > + * THREAD_INFO_IN_TASK is set. Instead of using task_struct we're > + * using TI_CPU which is extracted from asm-offsets.h by kbuild to get > + * the current processor ID. > + * > + * This also needs to be safeguarded when building asm-offsets.s > + * because at that time TI_CPU is not defined yet. > + */ > +#ifndef _TI_CPU > +#define raw_smp_processor_id() (0) > +#else > +#define raw_smp_processor_id() \ > + (*(unsigned int *)((void *)current_thread_info() + _TI_CPU)) > +#endif > > struct seq_file; > As I stated before, I would really like to avoid using this hack - I don't think we need to.