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X-CSE-ConnectionGUID: irLj4PscRDi7xbSptEqmiA== X-CSE-MsgGUID: q3Cehmh7R0mc6aH76nqA+g== X-IronPort-AV: E=McAfee;i="6800,10657,11841"; a="101986139" X-IronPort-AV: E=Sophos;i="6.25,154,1779174000"; d="scan'208";a="101986139" Received: from fmviesa009.fm.intel.com ([10.60.135.149]) by orvoesa102.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jul 2026 07:19:50 -0700 X-CSE-ConnectionGUID: Bhu909OcTi2Jw8FWWspLNQ== X-CSE-MsgGUID: etPWERUSRBqiiOVfAtNJ+A== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.25,154,1779174000"; d="scan'208";a="249209989" Received: from gabaabhi-mobl2.amr.corp.intel.com (HELO [10.125.108.45]) ([10.125.108.45]) by fmviesa009-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 13 Jul 2026 07:19:47 -0700 Message-ID: Date: Mon, 13 Jul 2026 07:19:47 -0700 Precedence: bulk X-Mailing-List: linux-arch@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 10/34] x86: mm: carve out the generic compile-time folded pgtable case in effective_prot() To: Yeoreum Yun , 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 Cc: david@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 References: <20260713135614.1618183-1-yeoreum.yun@arm.com> <20260713135614.1618183-11-yeoreum.yun@arm.com> From: Dave Hansen Content-Language: en-US Autocrypt: addr=dave.hansen@intel.com; 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charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/13/26 06:55, Yeoreum Yun wrote: > We want to change how pXdp_get() works with generic compile-time folded > page tables. To prepare for that, rework effective_prot() to ignore any > folded page tables entries, as it will unconditionally get called by > ptdump core with pXd_val(pXdp_get()), and we really should be ignoring > that value for folded entries. > > For this, identify the first real page-table level and > update effective_prot only when the current entry is not folded. Nit: could you please clean up the "we's" and move over to imperative voice for the series? We're picky about it on the x86 side, but I do think it's generally a good preferred practice across the kernel. Also I really do think this made the code worse. effective_prot() is a pretty tidy function. This change more than doubles the size and is also basically the same block copied and pasted twice. Further, this does seem like it will stop filling out some of the st->prot_levels[] entries. That seems like it might break things. It definitely needs to be covered in the changelog. So, in the end, I'm not 100% sure what this is doing. Is it "optimizing" the ptdump code? Or is it preemptively fixing code that will soon be throwing a compile error?