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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DD67CC433F5 for ; Wed, 1 Dec 2021 11:51:08 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243039AbhLALy3 (ORCPT ); Wed, 1 Dec 2021 06:54:29 -0500 Received: from foss.arm.com ([217.140.110.172]:34882 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S242696AbhLALy2 (ORCPT ); Wed, 1 Dec 2021 06:54:28 -0500 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id CF60A11B3; Wed, 1 Dec 2021 03:51:07 -0800 (PST) Received: from [10.57.0.220] (unknown [10.57.0.220]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 0E8A13F694; Wed, 1 Dec 2021 03:51:04 -0800 (PST) Subject: Re: [PATCH] percpu: km: ensure it is used with NOMMU (either UP or SMP) To: Dennis Zhou Cc: linux-arch-owner@vger.kernel.org, linux-mm@kvack.org, tj@kernel.org, cl@linux.com, akpm@linux-foundation.org, npiggin@gmail.com, hch@lst.de, arnd@arndb.de, linux-sh@vger.kernel.org, dalias@libc.org, linux-riscv@lists.infradead.org References: <20211130172954.129587-1-vladimir.murzin@arm.com> <20211130172954.129587-2-vladimir.murzin@arm.com> From: Vladimir Murzin Message-ID: <8c2b4666-cf13-3735-be1e-b8a1c71df113@arm.com> Date: Wed, 1 Dec 2021 11:51:04 +0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-sh@vger.kernel.org Hi, On 11/30/21 5:41 PM, Dennis Zhou wrote: > Hello, > > On Tue, Nov 30, 2021 at 05:29:54PM +0000, Vladimir Murzin wrote: >> Currently, NOMMU pull km allocator via !SMP dependency because most of >> them are UP, yet for SMP+NOMMU vm allocator gets pulled which: >> >> * may lead to broken build [1] >> * ...or not working runtime due to [2] >> >> It looks like SMP+NOMMU case was overlooked in bbddff054587 ("percpu: >> use percpu allocator on UP too") so restore that. >> >> [1] >> For ARM SMP+NOMMU (R-class cores) >> >> arm-none-linux-gnueabihf-ld: mm/percpu.o: in function `pcpu_post_unmap_tlb_flush': >> mm/percpu-vm.c:188: undefined reference to `flush_tlb_kernel_range' >> >> [2] >> static inline >> int vmap_pages_range_noflush(unsigned long addr, unsigned long end, >> pgprot_t prot, struct page **pages, unsigned int page_shift) >> { >> return -EINVAL; >> } >> >> Signed-off-by: Vladimir Murzin >> --- >> mm/Kconfig | 3 +-- >> 1 file changed, 1 insertion(+), 2 deletions(-) >> >> diff --git a/mm/Kconfig b/mm/Kconfig >> index d16ba92..66331e0 100644 >> --- a/mm/Kconfig >> +++ b/mm/Kconfig >> @@ -425,9 +425,8 @@ config THP_SWAP >> # UP and nommu archs use km based percpu allocator >> # >> config NEED_PER_CPU_KM >> - depends on !SMP >> bool >> - default y >> + default !SMP || !MMU >> > > Should this be `depends on !SMP || !MMU` with default yes? Because with > SMP && MMU, it shouldn't be an option to run with percpu-km. IIUC these are equivalent, truth table would not change if is under "depends" or "default" SMP MMU NEED_PER_CPU_KM y y !y || !y => n || n => n y n !y || !n => n || y => y n y !n || !y => y || n => y n n !n || !n => y || y => y > >> config CLEANCACHE >> bool "Enable cleancache driver to cache clean pages if tmem is present" >> -- >> 2.7.4 >> > > It's interesting to me that this is all coming up at once. Earlier this > month I had the same conversation with people involved with sh [1]. > > [1] https://lore.kernel.org/linux-sh/YY7tp5attRyK42Zk@fedora/ > > I can pull this shortly once I see whatever happened to linux-sh. Ahh, good to know! Adding SH folks here (start of discussion [0]). I see you came to the same conclusion, right? IIRC, RISC-V also have SMP+NOMMU, so adding them as well. [0] https://lore.kernel.org/linux-mm/20211130172954.129587-1-vladimir.murzin@arm.com/T/ Cheers Vladimir > > Thanks, > Dennis >