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 7A40AC433EF for ; Wed, 6 Jul 2022 16:17:47 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232833AbiGFQRr (ORCPT ); Wed, 6 Jul 2022 12:17:47 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:45250 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232248AbiGFQRq (ORCPT ); Wed, 6 Jul 2022 12:17:46 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 85283275FB; Wed, 6 Jul 2022 09:17:45 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 28BB1617B6; Wed, 6 Jul 2022 16:17:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id DB619C3411C; Wed, 6 Jul 2022 16:17:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1657124264; bh=iUXQ5zeCn7F+rXGeQUyYPSpHic8CAZ/oIMDK22tyFWQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=QkkCc5ixzpkLNHQqiXnFn3xxqX9vX6/7pjTO+beEcU7867jQ3yUN0tTRIumCfmw+l XIzzqW2j9D9B4/2+IOEa8BfZuC023EPkTIIlI8emhIRxwe64emyKhFAv8lGeUgTcta zuKnzfTcaivcT4wJUjtBnHQQwH0fDfbzXEQueHNwys3LxQLZfsPGxzK6XZS8PPJ8Yv t7y/jusImrBI66nsaI/PsqnHq6INlZtHblL2bL1nkSyj1G94GXsiCOgO9K8+nIKVlU JtGIYAGbNiHAni7AOCmeuagLTlruDxGIa8OywwwNA7QEwHE9BvWtCfy+YX0GOinCgL usB4BDoSQG4Xg== Date: Wed, 6 Jul 2022 17:17:37 +0100 From: Will Deacon To: Huacai Chen Cc: Dan Williams , Huacai Chen , Arnd Bergmann , Thomas Bogendoerfer , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Catalin Marinas , loongarch@lists.linux.dev, linux-arch , Xuefeng Li , Guo Ren , Xuerui Wang , Jiaxun Yang , Andrew Morton , Linux-MM , "open list:MIPS" , LKML , linux-arm-kernel , Feiyang Chen Subject: Re: [PATCH V4 3/4] mm/sparse-vmemmap: Generalise vmemmap_populate_hugepages() Message-ID: <20220706161736.GC3204@willie-the-truck> References: <20220704112526.2492342-1-chenhuacai@loongson.cn> <20220704112526.2492342-4-chenhuacai@loongson.cn> <20220705092937.GA552@willie-the-truck> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Precedence: bulk List-ID: X-Mailing-List: linux-mips@vger.kernel.org On Tue, Jul 05, 2022 at 09:07:59PM +0800, Huacai Chen wrote: > On Tue, Jul 5, 2022 at 5:29 PM Will Deacon wrote: > > On Mon, Jul 04, 2022 at 07:25:25PM +0800, Huacai Chen wrote: > > > diff --git a/mm/sparse-vmemmap.c b/mm/sparse-vmemmap.c > > > index 33e2a1ceee72..6f2e40bb695d 100644 > > > --- a/mm/sparse-vmemmap.c > > > +++ b/mm/sparse-vmemmap.c > > > @@ -686,6 +686,60 @@ int __meminit vmemmap_populate_basepages(unsigned long start, unsigned long end, > > > return vmemmap_populate_range(start, end, node, altmap, NULL); > > > } > > > > > > +void __weak __meminit vmemmap_set_pmd(pmd_t *pmd, void *p, int node, > > > + unsigned long addr, unsigned long next) > > > +{ > > > +} > > > + > > > +int __weak __meminit vmemmap_check_pmd(pmd_t *pmd, int node, unsigned long addr, > > > + unsigned long next) > > > +{ > > > + return 0; > > > +} > > > + > > > +int __meminit vmemmap_populate_hugepages(unsigned long start, unsigned long end, > > > + int node, struct vmem_altmap *altmap) > > > +{ > > > + unsigned long addr; > > > + unsigned long next; > > > + pgd_t *pgd; > > > + p4d_t *p4d; > > > + pud_t *pud; > > > + pmd_t *pmd; > > > + > > > + for (addr = start; addr < end; addr = next) { > > > + next = pmd_addr_end(addr, end); > > > + > > > + pgd = vmemmap_pgd_populate(addr, node); > > > + if (!pgd) > > > + return -ENOMEM; > > > + > > > + p4d = vmemmap_p4d_populate(pgd, addr, node); > > > + if (!p4d) > > > + return -ENOMEM; > > > + > > > + pud = vmemmap_pud_populate(p4d, addr, node); > > > + if (!pud) > > > + return -ENOMEM; > > > + > > > + pmd = pmd_offset(pud, addr); > > > + if (pmd_none(READ_ONCE(*pmd))) { > > > + void *p; > > > + > > > + p = vmemmap_alloc_block_buf(PMD_SIZE, node, altmap); > > > + if (p) { > > > + vmemmap_set_pmd(pmd, p, node, addr, next); > > > + continue; > > > + } else if (altmap) > > > + return -ENOMEM; /* no fallback */ > > > > Why do you return -ENOMEM if 'altmap' here? That seems to be different to > > what we currently have on arm64 and it's not clear to me why we're happy > > with an altmap for the pmd case, but not for the pte case. > The generic version is the same as X86. It seems that ARM64 always > fallback whether there is an altmap, but X86 only fallback in the no > altmap case. I don't know the reason of X86, can Dan Williams give > some explaination? Right, I think we need to understand the new behaviour here before we adopt it on arm64. Will