From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D1A4A399003; Mon, 27 Jul 2026 15:28:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785166092; cv=none; b=qvL5KWq0bQarTVvTE1FRFK0KHTK/JxBHov6Z458ydl/MR0jjpsh1BzFdo8IyZGDlC1L4w7SMcV86ASJZA8vOGLEUZFclBNnB3RascYVFyOLTxL/jOqspelN8w6Kfs4kbiSTtflRJC/aVnqU1c2EMlDKpW1wuNC/hjLZUdyHwyFE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785166092; c=relaxed/simple; bh=Y+qQEanGZ3cEaekOrI+WRbGJIXwLPORLRkgp5G2Leh4=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=qwsBqvou3t0WXjWS7vKE+FkXx56PH8ZlDXvEKnTwEwPO31GDUMIgLaqi9Y1LaoA3DbeekhcUnCrp3SI8kqCM8pvfvzK90LsSdGGgpWPpmb7aMRfwsVabX6ikmhqp11ZKEAPza6N5JwwseUQ2CgwkNjlMTlNBh+mGW+kS9guTyHo= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=MpTXTUf1; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="MpTXTUf1" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 876871F000E9; Mon, 27 Jul 2026 15:27:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1785166090; bh=Yn7THn92ltfwpRSIf8y0JNhszbsvPepGxqi4mlY8vZY=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=MpTXTUf1IbaWg0rNqCCbuu5PcPLoQsBp2p6QMOuOa6C67s0n3nqjMhVlRoe5gZoOp +9aLBlLFOAQK+U+e1a/cBUO3wj8+0KDmrYAdAak8VXXbUHQGCyoArrETZVpKuxnhKc 84kpzIlC6XXpyg48j/G5uzn147tOg0iJRP3njbel+YBW112yQFQfx4muGjeKrReHmW r2Xwn5pH7jKH2QupVAX0Nog8210kBR9DZuh7FpjJrb0lVwP1W66fZ+De2pTAnxOrsK IKIAMET39ImFYc2PoHOQVINhU4OXYzMcPNunD547s8eqzIr0pQ8Q9+tXOLuKYxmNGu Olgr4Wr0j5tHw== Message-ID: Date: Mon, 27 Jul 2026 17:27:52 +0200 Precedence: bulk X-Mailing-List: linux-mips@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RFC v2 13/20] x86: mm: carve out the generic compile-time folded pgtable case in effective_prot() To: Yeoreum Yun , Dave Hansen Cc: Russell King , Huacai Chen , WANG Xuerui , Thomas Bogendoerfer , Catalin Marinas , Will Deacon , Arnd Bergmann , Andrew Morton , Kairui Song , Qi Zheng , Shakeel Butt , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Johannes Weiner , Michal Hocko , Lorenzo Stoakes , Tianrui Zhao , Bibo Mao , Anup Patel , Atish Patra , Paul Walmsley , Palmer Dabbelt , Albert Ou , Alexandre Ghiti , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , x86@kernel.org, "H. Peter Anvin" , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jonas Bonn , Stefan Kristiansson , Stafford Horne , linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, kvm@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, linux-openrisc@vger.kernel.org References: <20260722-dummy_ptxp3-v2-0-d9e4bad31e0a@arm.com> <20260722-dummy_ptxp3-v2-13-d9e4bad31e0a@arm.com> <33c774f6-2750-4831-8eee-e43dc471da32@intel.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 7/22/26 23:00, Yeoreum Yun wrote: > On Wed, Jul 22, 2026 at 01:20:39PM -0700, Dave Hansen wrote: >> On 7/22/26 10:37, Yeoreum Yun wrote: >>> However, mm_pXd_folded() requires to mm for other architecture like >>> s390. might save the mm instead of first_level and calls the >>> ptdump_pt_level_first() with static inline version would make the >>> constant comparison. So it requires to save *mm* structure in here. >> >> I'm having a really hard time parsing that. >> >> I think you're trying to say that the effective_prot_p*() functions need >> to know the first level but they don't (today) need the mm_struct. If >> they don't get the (calculated) first_level passed in, they need the >> mm_struct instead. >> >> I think you're arguing 'pg_state' needs a ->first_level or a ->mm. >> Having a pg_state->mm doesn't seem bad to me at all. >> >> But, it's also a little bit silly. It would not be rocket science to >> pass an mm_struct down to the effective_prot_p*() functions. It makes a >> whole lot of sense to me for a page table walking function to need >> metadata from the mm_struct to walk correctly. > > Yes. I mean to add pg_state->mm like: > > diff --git a/arch/x86/mm/dump_pagetables.c b/arch/x86/mm/dump_pagetables.c > index 2afa7a23340e..aaf00f0c6624 100644 > --- a/arch/x86/mm/dump_pagetables.c > +++ b/arch/x86/mm/dump_pagetables.c > @@ -38,6 +38,7 @@ struct pg_state { > bool check_wx; > unsigned long wx_pages; > struct seq_file *seq; > + struct mm_struct *mm; > }; > > struct addr_marker { > @@ -254,7 +255,7 @@ static void effective_prot(struct ptdump_state *pt_st, int level, u64 val) > pgprotval_t prot = val & PTE_FLAGS_MASK; > pgprotval_t effective; > > - if (level > 0) { > + if (level > pgtable_first_level(st->mm)) { > pgprotval_t higher_prot = st->prot_levels[level - 1]; > > effective = (higher_prot & prot & (_PAGE_USER | _PAGE_RW)) | > @@ -452,7 +453,8 @@ bool ptdump_walk_pgd_level_core(struct seq_file *m, > .level = -1, > .to_dmesg = dmesg, > .check_wx = checkwx, > - .seq = m > + .seq = m, > + .mm = mm, > }; > > ptdump_walk_pgd(&st.ptdump, mm, pgd); > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index 8c093c119e5a..6e7d0580db99 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -2490,4 +2490,15 @@ pgprot_t vm_get_page_prot(vm_flags_t vm_flags) \ > } \ > EXPORT_SYMBOL(vm_get_page_prot); > > +static inline int pgtable_first_level(struct mm_struct *mm) > +{ > + if (mm_pmd_folded(mm)) > + return 3; > + if (mm_pud_folded(mm)) > + return 2; > + if (mm_p4d_folded(mm)) > + return 1; > + return 0; > +} In that case the function should probably be called "mm_first_pgtable_level" But now it gets confusing, because we have enum pgtable_level { PGTABLE_LEVEL_PTE = 0, PGTABLE_LEVEL_PMD, PGTABLE_LEVEL_PUD, PGTABLE_LEVEL_P4D, PGTABLE_LEVEL_PGD, }; But maybe we can make sense of it and do /* * The enum values correspond to the numerical page table level, * starting with the highest level being level 0. */ enum pgtable_level { PGTABLE_LEVEL_PGD = 0, PGTABLE_LEVEL_P4D, PGTABLE_LEVEL_PUD, PGTABLE_LEVEL_PMD, PGTABLE_LEVEL_PTE, }; static inline enum pgtable_level mm_first_pgtable_level(struct mm_struct *mm) { if (mm_pmd_folded(mm)) return PGTABLE_LEVEL_PMD; if (mm_pud_folded(mm)) return PGTABLE_LEVEL_PUD; if (mm_p4d_folded(mm)) return PGTABLE_LEVEL_P4D; return PGTABLE_LEVEL_PGD; } We could even teach effective_prot() and friends to consume enum pgtable_level now and have it all be a bit cleaner? -- Cheers, David