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[173.68.57.129]) by smtp.gmail.com with ESMTPSA id n20sm2988821qkp.65.2021.12.03.13.02.05 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Dec 2021 13:02:06 -0800 (PST) Date: Fri, 3 Dec 2021 16:02:03 -0500 From: Dennis Zhou To: Vladimir Murzin Cc: Dennis Zhou , 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 Subject: Re: [PATCH] percpu: km: ensure it is used with NOMMU (either UP or SMP) Message-ID: References: <20211130172954.129587-1-vladimir.murzin@arm.com> <20211130172954.129587-2-vladimir.murzin@arm.com> <8c2b4666-cf13-3735-be1e-b8a1c71df113@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <8c2b4666-cf13-3735-be1e-b8a1c71df113@arm.com> X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 74636801AB05 X-Stat-Signature: 5nnskif9b6kqbe3wro4pnptrc9zw9x7k Authentication-Results: imf06.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=kernel.org (policy=none); spf=pass (imf06.hostedemail.com: domain of dennisszhou@gmail.com designates 209.85.219.48 as permitted sender) smtp.mailfrom=dennisszhou@gmail.com X-HE-Tag: 1638565327-945546 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, Dec 01, 2021 at 11:51:04AM +0000, Vladimir Murzin wrote: > 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 > I may be wrong, but I think this is slightly different as we're using #ifdef / #if defined(). > > > >> 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? > Yeah, I don't see anything else from linux-sh. So I'll go ahead and apply this with my change if you're fine with that. > 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