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,URIBL_BLOCKED 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 2B984C433EF for ; Sun, 5 Sep 2021 20:25:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id F2EF460F9D for ; Sun, 5 Sep 2021 20:25:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234827AbhIEU0x (ORCPT ); Sun, 5 Sep 2021 16:26:53 -0400 Received: from mail.kernel.org ([198.145.29.99]:50724 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230217AbhIEU0w (ORCPT ); Sun, 5 Sep 2021 16:26:52 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id AC3DA61051 for ; Sun, 5 Sep 2021 20:25:48 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1630873548; bh=jvqK5MOKEiuMUZfVYv70SUUKMTKBzqnrpLUINlYxDsU=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=TrrFpNTRjjO2Hz6hHKo0KVQDmU/GY/zOTyS7r6ARsshI6wPHirjRc0Eks491twNMX Ph5htjryZP973ZzzTA3aCkC/cVWe1BDLhJANGjXGcB8fLyrW+5Xy31+dndlMc9wFO8 3b7LeUK9gQvCIGX/BATmWo8xCdl9amA9QAHAbYB3qABGeTbx1HBWQxQyDbFK7UoCVY m0lw3x07SxUTaDf78v08UgDOe+SbGpjU0cJR0Wi4tT+e7bPx2Qp2I7gCbXZd2Nkkh3 xyxfsOHPPcXjA4O8yZgdtFFd5rTnxuqbjlkMyNspGom8RoNuaEN1ZTfmp4REqiKkZ5 k83LtiXGxMFCw== Received: by mail-ot1-f47.google.com with SMTP id g66-20020a9d12c8000000b0051aeba607f1so6145230otg.11 for ; Sun, 05 Sep 2021 13:25:48 -0700 (PDT) X-Gm-Message-State: AOAM532uXBIhUYgtNGSQUVmH6GHhcHQm4KULt19ejiS+0XQbtQxtHcR2 OIIp0VmCD7CpNNF9L/fg9LljuFAp/QMxV7iJAJk= X-Google-Smtp-Source: ABdhPJy5fGmipkk4mNMOPumV5B8kOcAihT0XXVmm7Nvg1N85HNF7sX8xq0TYQx90nueu1uHkjq8krLVFwkDWQ3XJT/o= X-Received: by 2002:a9d:200b:: with SMTP id n11mr8062882ota.30.1630873547870; Sun, 05 Sep 2021 13:25:47 -0700 (PDT) MIME-Version: 1.0 References: <20210902155429.3987201-1-keithp@keithp.com> <20210904060908.1310204-1-keithp@keithp.com> <20210904060908.1310204-2-keithp@keithp.com> In-Reply-To: <20210904060908.1310204-2-keithp@keithp.com> From: Ard Biesheuvel Date: Sun, 5 Sep 2021 22:25:37 +0200 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: [PATCH 1/3] ARM: Pass cpu number to secondary_start_kernel To: Keith Packard Cc: Linux Kernel Mailing List , Abbott Liu , Alexander Sverdlin , Andrew Morton , Anshuman Khandual , Arnd Bergmann , Bjorn Andersson , Florian Fainelli , Geert Uytterhoeven , Hartley Sweeten , Jens Axboe , Jian Cai , Joe Perches , Kees Cook , Krzysztof Kozlowski , Linus Walleij , Linux ARM , Manivannan Sadhasivam , Marc Zyngier , Masahiro Yamada , Miguel Ojeda , Mike Rapoport , Nathan Chancellor , Nick Desaulniers , Nicolas Pitre , Rob Herring , Russell King , Thomas Gleixner , =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= , Valentin Schneider , Viresh Kumar , "Wolfram Sang (Renesas)" , YiFei Zhu , Keith Packard Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi Keith, This looks like a worthwhile cleanup to me regardless of the following patches. On Sat, 4 Sept 2021 at 08:09, Keith Packard wrote: > > Instead of pulling the CPU value out of the thread_info struct, pass > it as an argument. When first initializing secondary processors, this > is done by stashing the value in the secondary_data struct. When > restarting idle processors, the previous CPU value is passed. > > Because the cpu is now known at the top of secondary_start_kernel, the > per_cpu_offset value can now be set at this point, instead of in > cpu_init where it was also incorrectly setting the per_cpu_offset for > the boot processor before that value had been computed. > > Signed-off-by: Keith Packard Reviewed-by: Ard Biesheuvel > --- > arch/arm/include/asm/smp.h | 3 ++- > arch/arm/kernel/head-nommu.S | 1 + > arch/arm/kernel/head.S | 1 + > arch/arm/kernel/setup.c | 6 ------ > arch/arm/kernel/smp.c | 14 +++++++++----- > 5 files changed, 13 insertions(+), 12 deletions(-) > > diff --git a/arch/arm/include/asm/smp.h b/arch/arm/include/asm/smp.h > index 5d508f5d56c4..86a7fd721556 100644 > --- a/arch/arm/include/asm/smp.h > +++ b/arch/arm/include/asm/smp.h > @@ -48,7 +48,7 @@ extern void set_smp_ipi_range(int ipi_base, int nr_ipi); > * Called from platform specific assembly code, this is the > * secondary CPU entry point. > */ > -asmlinkage void secondary_start_kernel(void); > +asmlinkage void secondary_start_kernel(unsigned int cpu); > > > /* > @@ -61,6 +61,7 @@ struct secondary_data { > }; > unsigned long swapper_pg_dir; > void *stack; > + unsigned int cpu; > }; > extern struct secondary_data secondary_data; > extern void secondary_startup(void); > diff --git a/arch/arm/kernel/head-nommu.S b/arch/arm/kernel/head-nommu.S > index 0fc814bbc34b..5aa8ef42717f 100644 > --- a/arch/arm/kernel/head-nommu.S > +++ b/arch/arm/kernel/head-nommu.S > @@ -114,6 +114,7 @@ ENTRY(secondary_startup) > add r12, r12, r10 > ret r12 > 1: bl __after_proc_init > + ldr r0, [r7, #16] @ set up cpu number > ldr sp, [r7, #12] @ set up the stack pointer > mov fp, #0 > b secondary_start_kernel > diff --git a/arch/arm/kernel/head.S b/arch/arm/kernel/head.S > index 7f62c5eccdf3..0e541af738e2 100644 > --- a/arch/arm/kernel/head.S > +++ b/arch/arm/kernel/head.S > @@ -394,6 +394,7 @@ ENDPROC(secondary_startup_arm) > > ENTRY(__secondary_switched) > ldr_l r7, secondary_data + 12 @ get secondary_data.stack > + ldr_l r0, secondary_data + 16 @ get secondary_data.cpu > mov sp, r7 > mov fp, #0 > b secondary_start_kernel > diff --git a/arch/arm/kernel/setup.c b/arch/arm/kernel/setup.c > index 73ca7797b92f..ca0201635fac 100644 > --- a/arch/arm/kernel/setup.c > +++ b/arch/arm/kernel/setup.c > @@ -532,12 +532,6 @@ void notrace cpu_init(void) > BUG(); > } > > - /* > - * This only works on resume and secondary cores. For booting on the > - * boot cpu, smp_prepare_boot_cpu is called after percpu area setup. > - */ > - set_my_cpu_offset(per_cpu_offset(cpu)); > - > cpu_proc_init(); > > /* > diff --git a/arch/arm/kernel/smp.c b/arch/arm/kernel/smp.c > index 74679240a9d8..55cb1689a4b3 100644 > --- a/arch/arm/kernel/smp.c > +++ b/arch/arm/kernel/smp.c > @@ -153,6 +153,7 @@ int __cpu_up(unsigned int cpu, struct task_struct *idle) > secondary_data.pgdir = virt_to_phys(idmap_pgd); > secondary_data.swapper_pg_dir = get_arch_pgd(swapper_pg_dir); > #endif > + secondary_data.cpu = cpu; > sync_cache_w(&secondary_data); > > /* > @@ -373,11 +374,14 @@ void arch_cpu_idle_dead(void) > * cpu initialisation. There's some initialisation which needs > * to be repeated to undo the effects of taking the CPU offline. > */ > - __asm__("mov sp, %0\n" > + __asm__("mov r0, %1\n" > + " mov sp, %0\n" > " mov fp, #0\n" > " b secondary_start_kernel" > : > - : "r" (task_stack_page(current) + THREAD_SIZE - 8)); > + : "r" (task_stack_page(current) + THREAD_SIZE - 8), > + "r" (cpu) > + : "r0"); > } > #endif /* CONFIG_HOTPLUG_CPU */ > > @@ -400,10 +404,11 @@ static void smp_store_cpu_info(unsigned int cpuid) > * This is the secondary CPU boot entry. We're using this CPUs > * idle thread stack, but a set of temporary page tables. > */ > -asmlinkage void secondary_start_kernel(void) > +asmlinkage void secondary_start_kernel(unsigned int cpu) > { > struct mm_struct *mm = &init_mm; > - unsigned int cpu; > + > + set_my_cpu_offset(per_cpu_offset(cpu)); > > secondary_biglittle_init(); > > @@ -420,7 +425,6 @@ asmlinkage void secondary_start_kernel(void) > * All kernel threads share the same mm context; grab a > * reference and switch to it. > */ > - cpu = smp_processor_id(); > mmgrab(mm); > current->active_mm = mm; > cpumask_set_cpu(cpu, mm_cpumask(mm)); > -- > 2.33.0 >