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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9ACBCC44501 for ; Tue, 14 Jul 2026 16:51:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=UaA1m6+mryjjVSTgff8k5u3l9bigH1hhQ1N9JFF99rU=; b=NYlzFgRVcyZq1W VhbmNLzkLc4B6pLgFJCvx4oDmMAn2rE9y8qZx5vap1xa/9SWmSwGu751qDSXb/gHjdfy3MyxqaxPK L5NKJ6bwNk+ik4AgHk0elxWSnMaDsv/BjYX0zWtHUlF0H574qE2HtEBTt0LZ2BiB72FtF3zEJAgHV 67cYDxFcD4AHRzrWO2oeTwg0lVhKLiud3Tn0nr6L4+sbQIs4cg9UwRcFQysOpFFtyI42I58W7u8sj 2FVS4Lw3W9oi9qyCGR/0haNK9mdm20izBpU5PQd567zcfbBp8oXEsOJ42t6NxIYUtCJa75btiFKX8 eADyXU5BRCU/DzSeRkiw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wjgLq-0000000CgcN-0kFg; Tue, 14 Jul 2026 16:51:22 +0000 Received: from desiato.infradead.org ([2001:8b0:10b:1:d65d:64ff:fe57:4e05]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wjgLo-0000000Cgc0-2QUR; Tue, 14 Jul 2026 16:51:20 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=desiato.20200630; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=JFYx/PcJYBHS7M9Y27BjGgk5pg7WT/rEUT06432k7IQ=; b=q8v9f4uKI+lt44eHeblLyPuEIw qSv19fGfCD22HFIbx9Iiw51EqTdC+QxjtNcldJYf8hs0LzImqaobs+F8/BjsdDXB61vJAMyrvCFa/ VjULjHyHWlENbVzqLpI5XUU+Uc2nxxXhQDVrkNFkan0Ny/BRJzvEc1f836Z4ryA0HVloU+omXSYOY ozamEE4kziA22rZDRFmw8bSlc4HxSRa4/BgiwcPCKvc8v31KYBQ14yGLWWquSK9ki1NOuCnMe2AXl NNeEWLCIquCT8QXMZVFASRn2O8EwMTchWFqGdmvjl9MkO3xV4fOHQEOG2WYvNqFf/IyPbPIYNzqML 4NsO/tNA==; Received: from foss.arm.com ([217.140.110.172]) by desiato.infradead.org with esmtp (Exim 4.99.2 #2 (Red Hat Linux)) id 1wjgLl-0000000Chjm-1rg2; Tue, 14 Jul 2026 16:51:19 +0000 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 34AC11477; Tue, 14 Jul 2026 09:51:10 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.2.213.3]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 92B183F7B4; Tue, 14 Jul 2026 09:51:03 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784047873; bh=UvBhg+nD12g2Xn0O2D0o4P28bmGT2yfpQKOxtSEnl1I=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=LJE9GnqgPAJTHNyrHvXiGytDU8Y+XMmq5qcc7VQwk9xF51NV6qToYp1rk0iHEdw2c SQefERcHjF0VMLdrLpD4VYdyPuCv0noF41iChasEg/du+6t2wy8gA1iDS6Ph+r4Igc KCRrQeoHcKvxhPGR+tFzzHZ+eCmo3MvDkxCNZGoc= Date: Tue, 14 Jul 2026 17:51:01 +0100 From: Yeoreum Yun To: Dave Hansen Cc: Yeoreum Yun , "David Hildenbrand (Arm)" , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux@armlinux.org.uk, akpm@linux-foundation.org, ankur.a.arora@oracle.com, rppt@kernel.org, linmag7@gmail.com, chleroy@kernel.org, klarasmodin@gmail.com, chenhuacai@kernel.org, kernel@xen0n.name, kas@kernel.org, zhangtianyang@loongson.cn, wangyuli@aosc.io, tsbogend@alpha.franken.de, ljs@kernel.org, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, ryan.roberts@arm.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, baolin.wang@linux.alibaba.com, tj@kernel.org, kevin.brodsky@arm.com, anup@brainfault.org, atish.patra@linux.dev, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, anshuman.khandual@arm.com, yang@os.amperecomputing.com, chaitanyas.prakash@arm.com, ardb@kernel.org, guoren@kernel.org, yang.li85200@gmail.com, viro@zeniv.linux.org.uk, dinguyen@kernel.org, schuster.simon@siemens-energy.com, wangruikang@iscas.ac.cn, junhui.liu@pigmoral.tech, muchun.song@linux.dev, vishal.moola@gmail.com, namcao@linutronix.de, pavel@kernel.org, djbw@kernel.org, yu-cheng.yu@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, coxu@redhat.com, andreas@gaisler.com, liam@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, geert@linux-m68k.org, shorne@gmail.com, jonas@southpole.se, stefan.kristiansson@saunalahti.fi Subject: Re: [RFC PATCH 10/34] x86: mm: carve out the generic compile-time folded pgtable case in effective_prot() Message-ID: References: <6007625e-c3f9-4ad6-99a8-61396bccbcec@kernel.org> <32d459d1-ad19-4baf-bbb1-0565458001d2@intel.com> <3ea30f8a-bb29-4bf5-8400-1c4840d46a88@kernel.org> <7e84b200-25eb-43a6-b5e2-5f27f2d82a77@intel.com> <31988089-095a-4eed-b5e2-c677c70f79f6@kernel.org> <14e250db-1641-4085-8d13-02f819657d5f@intel.com> <6df814c9-405c-48d8-96ea-929c4b28949b@intel.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260714_175117_849713_A23B02BF X-CRM114-Status: GOOD ( 25.49 ) X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org On Tue, Jul 14, 2026 at 05:08:24PM +0100, Yeoreum Yun wrote: > On Tue, Jul 14, 2026 at 07:35:19AM -0700, Dave Hansen wrote: > > On 7/14/26 04:40, Yeoreum Yun wrote: > > > @@ -254,22 +255,8 @@ static void effective_prot(struct ptdump_state *pt_st, int level, u64 val) > > > struct pg_state *st = container_of(pt_st, struct pg_state, ptdump); > > > pgprotval_t prot = val & PTE_FLAGS_MASK; > > > pgprotval_t effective; > > > - bool first_level = false; > > > > > > - /* Ignore folded levels ... */ > > > - if (((level == 0) && mm_p4d_folded(st->mm)) || > > > - ((level == 1) && mm_pud_folded(st->mm)) || > > > - ((level == 2) && mm_pmd_folded(st->mm))) > > > - return; > > > - > > > - /* ... and make the actual first level remember the protection. */ > > > - if (((level == 0)) || > > > - ((level == 1) && mm_p4d_folded(st->mm)) || > > > - ((level == 2) && mm_pud_folded(st->mm)) || > > > - ((level == 3) && mm_pmd_folded(st->mm))) > > > - first_level = true; > > > - > > > - if (!first_level) { > > > + if (first_level > st->first_level) { > > > pgprotval_t higher_prot = st->prot_levels[level - 1]; > > > > > > effective = (higher_prot & prot & (_PAGE_USER | _PAGE_RW)) | > > > @@ -471,6 +458,15 @@ bool ptdump_walk_pgd_level_core(struct seq_file *m, > > > .seq = m > > > }; > > > > > > + if (mm_pmd_folded (mm)) > > > + st->first_level = 3; > > > + else if (mm_pud_folded (mm)) > > > + st->first_level = 2; > > > + else if (mm_p4d_folded (mm)) > > > + st->first_level = 1; > > > + else > > > + st->first_level = 0; > > > + > > > ptdump_walk_pgd(&st.ptdump, mm, pgd); > > > > This is indeed an improvement and a step in the right direction! Thanks > > for looking at this. > > > > But one of my test for whether it's good x86 code is whether there's any > > actually x86-specific logic in it. Isn't this basically a translation > > between the integer level number and whether it is folded? > > > > That seems like a common helper that more than one arch could use. Could > > this be stuck in a helper so that all arch/x86 has to do is: > > > > if (mm_pt_level_folded(mm, level)) > > return; > > Yes. at least the level semantic in ptdump (pgd is level 0, > p4d is level 1, ...) is same to all archs where use ptdump. > So It seems reasonable to add this common helper in ptdump.c > Furthermore, the effective_prot() need to require to identify whether it's the first pgtable to prevent the inheriting from dummy value. So I think it seems to make a ptdump_pt_level_first() like: diff --git a/mm/ptdump.c b/mm/ptdump.c index 973020000096c..2ec5700e4be5e 100644 --- a/mm/ptdump.c +++ b/mm/ptdump.c @@ -190,6 +190,23 @@ void ptdump_walk_pgd(struct ptdump_state *st, struct mm_struct *mm, pgd_t *pgd) st->note_page_flush(st); } +bool pdtump_pt_level_first(struct mm_struct *mm, int level) +{ + if (!mm || level > CONFIG_PGTABLE_LEVELS) + return false; + + if (mm_pmd_folded(mm) && level == 3) + return true; + if (mm_pud_folded(mm) && level == 2) + return true; + if (mm_p4d_folded(mm) && level == 1) + return true; + if (level == 0) + return true; + + return false; +} -- Sincerely, Yeoreum Yun _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv