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 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id ACEC5C433EF for ; Thu, 11 Nov 2021 00:53:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 85F3261381 for ; Thu, 11 Nov 2021 00:53:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230430AbhKKA4G (ORCPT ); Wed, 10 Nov 2021 19:56:06 -0500 Received: from brightrain.aerifal.cx ([216.12.86.13]:51844 "EHLO brightrain.aerifal.cx" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230311AbhKKA4F (ORCPT ); Wed, 10 Nov 2021 19:56:05 -0500 Date: Wed, 10 Nov 2021 19:53:13 -0500 From: Rich Felker To: Rob Landley Cc: Linux-sh list , Nicholas Piggin , Dennis Zhou , Geert Uytterhoeven Subject: Re: [PATCH] Fix the j-core SOC build. Message-ID: <20211111005312.GM7074@brightrain.aerifal.cx> References: <7d559bd1-1f9c-124f-ad4d-c805c049971a@landley.net> <20211003021851.GA2559@brightrain.aerifal.cx> <20211110213345.GK7074@brightrain.aerifal.cx> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211110213345.GK7074@brightrain.aerifal.cx> User-Agent: Mutt/1.5.21 (2010-09-15) Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org On Wed, Nov 10, 2021 at 04:33:46PM -0500, Rich Felker wrote: > On Sat, Oct 02, 2021 at 10:18:51PM -0400, Rich Felker wrote: > > On Sat, Oct 02, 2021 at 02:32:15PM -0500, Rob Landley wrote: > > > From: Rob Landley > > > > > > Commit b67177ecd956 broke the j-core SOC build with a link failure, because > > > mm/percpu.c function pcpu_post_unmap_tlb_flush() calls flush_tlb_kernel_range() > > > which is defined under #ifdef CONFIG_MMU. > > > > > > Signed-off-by: Rob Landley > > > --- > > > > > > arch/sh/kernel/smp.c | 5 +++++ > > > 1 file changed, 5 insertions(+) > > > > > > diff --git a/arch/sh/kernel/smp.c b/arch/sh/kernel/smp.c > > > index 65924d9ec245..3ec8f32aad85 100644 > > > --- a/arch/sh/kernel/smp.c > > > +++ b/arch/sh/kernel/smp.c > > > @@ -468,4 +468,9 @@ void flush_tlb_one(unsigned long asid, unsigned long vaddr) > > > local_flush_tlb_one(asid, vaddr); > > > } > > > > > > +#else > > > +void flush_tlb_kernel_range(unsigned long start, unsigned long end) > > > +{ > > > + local_flush_tlb_all(); > > > +} > > > #endif > > > > local_flush_tlb_all() is defined in arch/sh/mm/nommu.c as BUG(); so > > this is most likely wrong unless it just doesn't get called. I think > > there should probably be something at a very general level dummying > > out these functions/macros on nommu but I don't know where it should > > be. > > I've looked into this some more, and while arch/arm does dummy its > equivalent functions out on nommu, arch/sh has always had them as > BUG(), and indeed it makes some sense to catch erroneous usage. > pcpu_post_unmap_tlb_flush should probably have the flush under #ifdef > CONFIG_MMU or something. > > I've added the author of the commit that broke this to Cc in case he > has any thoughts. I think we actually have the wrong commit to blame; it looks like 93274f1dd6b0 ("percpu: flush tlb in pcpu_reclaim_populated()") added the TLB flush. However, this rabbit hole seems to go a lot deeper. According to the comments in the files, percpu-km.c, not percpu-vm.c, is supposed to be used on nommu archs. However, mm/Kconfig has NEED_PER_CPU_KM depending on !SMP rather than !SMP || !MMU, which mismatches the comments in the source. So should we be trying to fix the Kconfig constraints to use -km? Or fixing -vm to work on nommu like it used to? Rich