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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 9F509FEA839 for ; Wed, 25 Mar 2026 09:55:34 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id CD7EF6B008C; Wed, 25 Mar 2026 05:55:33 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id C8E0E6B0092; Wed, 25 Mar 2026 05:55:33 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id B778A6B0093; Wed, 25 Mar 2026 05:55:33 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id A6AB26B008C for ; Wed, 25 Mar 2026 05:55:33 -0400 (EDT) Received: from smtpin08.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 5249EBAEBD for ; Wed, 25 Mar 2026 09:55:33 +0000 (UTC) X-FDA: 84584128146.08.A847AEB Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf08.hostedemail.com (Postfix) with ESMTP id 675E0160002 for ; Wed, 25 Mar 2026 09:55:31 +0000 (UTC) Authentication-Results: imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=imBvzxX9; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Authentication-Results: i=1; imf08.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=imBvzxX9; spf=pass (imf08.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1774432531; a=rsa-sha256; cv=none; b=4uH1fDS3N4I0x3+Z3t/hnIrVoSxcbXDOv/cOP/b+PgMPVJoAO3Ol9mclkm8KyRJvhI8uk5 O3I+Am7gKwlyIWwKjMHIMydqGMJJd8UPCmCbMk4/MxBprx/Y8Mnxi+VAb/vyLQ8a1Oqqbp tSquPvD9DnYhrwcDAT3RQEMgP5n4EoU= ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1774432531; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=H7vJC7UCokahSY6oGz+pBo6t4W8MPgVxZKg0ZaMQp0I=; b=N6SG5vO91lbSTLua/UAWmxO1ZDo8CadPhcKxG8b7peNtyg0bTx9iHRsFqnKesK2tDQfZso JIP7nNdPvpOI4xPhY2xoPyikvzY0mOBx7gv1LGhcWvob+cJxmYzFM96EytzgnRgpwS0FFt o2JG5yfJGw1WYo+nwjzuSlgLEMPPubU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 6485043345; Wed, 25 Mar 2026 09:55:30 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 09D20C4CEF7; Wed, 25 Mar 2026 09:55:26 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774432530; bh=9SU+G1pzNfkJYWyyJavSVZlDryVqXa7NO/5Yp1+Hwuw=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=imBvzxX9+0+DnwBNDpet8fwln6JuraH8UeljdObUd/dreDGMpuVgki8GeZzzgA0ZH UEEHqQjM5U224ArxpDQG887GBml3c6f2iUD/NMT3IGXrr0NyWJ/HKXxSjaONu1/BY6 MpNC+qIVdA6Cpxm18N8FeJe8hHeJL+S0Mhr/+C94T//PXLsSQruYgfnb/qUwKPZFs5 nAOdvVFm4risE9RhLWvnNsAblgkSRqz+4Ag+TeUglGR/y/J1hLhB+6+StjGhdpE47F SB5PEOKIc7sLFnTTVUf/+K1+x8sbYVgZjGuwCK2Gs/KxDlcSjel2O5nE2ef+qpPWT8 shCfc/A8KpMow== Message-ID: <44dd86c0-1845-4dd9-b4b4-2cef6d1c6357@kernel.org> Date: Wed, 25 Mar 2026 10:55:23 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 1/2] mm: make lazy MMU mode context-aware To: Alexander Gordeev , Kevin Brodsky , Andrew Morton , Gerald Schaefer , Heiko Carstens , Christian Borntraeger , Vasily Gorbik Cc: linux-s390@vger.kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: 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 X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: 675E0160002 X-Stat-Signature: xz8mnzu6rgepjcuqiyoshoboapbdugjz X-Rspam-User: X-HE-Tag: 1774432531-201287 X-HE-Meta: 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 HxgYKRjL gz/yBOBWd3TypXdFP2PSk+tZiRrxlS/aP8pM03kREp0wufxkSHZhMFMjzOSZTTGLO0FLp5bnjrLDtLHlVJAn55TaJwZNHFLwFRDQCoTqSyh/A6/Ojtg0jnefjF5/X7LUpwHbWOOaGQRReNKcOL6KmkB7cDBIZOF1evoh5GRR8zQj4ht6q055cqAjgJUhdxfO1lSHZsaJPTp1GrMboEoSkrpz27GLCGw1VyZjT9Wxr+AbJAeNSDYfHkuk0AyO/GKZF+0JrHfS43fKI06eL4ciUJLsIPbbxd39rhyCshbBWA4M4YR2LHNrN8FFBM0v6RPjfs4kY Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 3/25/26 08:41, Alexander Gordeev wrote: > Lazy MMU mode is assumed to be context-independent, in the sense > that it does not need any additional information while operating. > However, the s390 architecture benefits from knowing the exact > page table entries being modified. > > Introduce lazy_mmu_mode_enable_pte(), which is provided with the > process address space and the page table being operated on. This > information is required to enable s390-specific optimizations. > > The function takes parameters that are typically passed to page- > table level walkers, which implies that the span of PTE entries > never crosses a page table boundary. > > Architectures that do not require such information simply do not > need to define the arch_enter_lazy_mmu_mode_pte() callback. > > Signed-off-by: Alexander Gordeev > --- > fs/proc/task_mmu.c | 2 +- > include/linux/pgtable.h | 42 +++++++++++++++++++++++++++++++++++++++++ > mm/madvise.c | 8 ++++---- > mm/memory.c | 8 ++++---- > mm/mprotect.c | 2 +- > mm/mremap.c | 2 +- > mm/vmalloc.c | 6 +++--- > 7 files changed, 56 insertions(+), 14 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index e091931d7ca1..4e3b1987874a 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -2752,7 +2752,7 @@ static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, > return 0; > } > > - lazy_mmu_mode_enable(); > + lazy_mmu_mode_enable_pte(vma->vm_mm, start, end, start_pte); > > if ((p->arg.flags & PM_SCAN_WP_MATCHING) && !p->vec_out) { > /* Fast path for performing exclusive WP */ > diff --git a/include/linux/pgtable.h b/include/linux/pgtable.h > index a50df42a893f..481b45954800 100644 > --- a/include/linux/pgtable.h > +++ b/include/linux/pgtable.h > @@ -271,6 +271,44 @@ static inline void lazy_mmu_mode_enable(void) > arch_enter_lazy_mmu_mode(); > } > > +#ifndef arch_enter_lazy_mmu_mode_pte > +static inline void arch_enter_lazy_mmu_mode_pte(struct mm_struct *mm, > + unsigned long addr, > + unsigned long end, > + pte_t *ptep) Two tab alignment please. (applies to other things hwere as well) > +{ > + arch_enter_lazy_mmu_mode(); > +} > +#endif > + > +/** > + * lazy_mmu_mode_enable_pte() - Enable the lazy MMU mode with parameters You have to be a lot clearer about implications. For example, what happens if we would bail out and not process all ptes? What are the exact semantics. > + * > + * Enters a new lazy MMU mode section; if the mode was not already enabled, > + * enables it and calls arch_enter_lazy_mmu_mode_pte(). > + * > + * Must be paired with a call to lazy_mmu_mode_disable(). > + * > + * Has no effect if called: > + * - While paused - see lazy_mmu_mode_pause() > + * - In interrupt context > + */ > +static inline void lazy_mmu_mode_enable_pte(struct mm_struct *mm, > + unsigned long addr, > + unsigned long end, > + pte_t *ptep) It can be multiple ptes, so should this be some kind of "pte_range"/ lazy_mmu_mode_enable_for_pte_range() A bit mouthful but clearer. > +{ > + struct lazy_mmu_state *state = ¤t->lazy_mmu_state; > + > + if (in_interrupt() || state->pause_count > 0) > + return; > + > + VM_WARN_ON_ONCE(state->enable_count == U8_MAX); > + > + if (state->enable_count++ == 0) > + arch_enter_lazy_mmu_mode_pte(mm, addr, end, ptep); > +} I'm wondering whether that could instead be some optional interface that we trigger after the lazy_mmu_mode_enable. But looking at lazy_mmu_mode_enable() users, there don't seem to be cases where we would process multiple different ranges under a single enable() call, right? -- Cheers, David