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]) by smtp.lore.kernel.org (Postfix) with ESMTP id 818D0C46CD2 for ; Tue, 30 Jan 2024 08:32:07 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id F01046B009F; Tue, 30 Jan 2024 03:32:06 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id E8A546B00A1; Tue, 30 Jan 2024 03:32:06 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id D2B366B00A2; Tue, 30 Jan 2024 03:32:06 -0500 (EST) 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 BF65D6B009F for ; Tue, 30 Jan 2024 03:32:06 -0500 (EST) Received: from smtpin30.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 88C4DA1F84 for ; Tue, 30 Jan 2024 08:32:06 +0000 (UTC) X-FDA: 81735309852.30.C0CB8F8 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf20.hostedemail.com (Postfix) with ESMTP id 902151C0021 for ; Tue, 30 Jan 2024 08:32:04 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=none; spf=pass (imf20.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1706603524; 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; bh=jSEMVaK+rrlJNJ0zTwRLxVUfpM5jOWWKTKXrnzE7CEs=; b=iIoKvV/l3QswTsn3oPR4CZv4VxFDnHGAk4ebRt/s6FnENX70ejO00ElQunuylMjt113sTE DDHI0d5GgRGT+fwbxM5SwcQsE0mp4kCbR8VleAjPoHrLdqY/oQD7LtZwVrf7xq7K6uHbhu fwHE/+EOSZgPeBc8V+0JGooT4gAz1NQ= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706603524; a=rsa-sha256; cv=none; b=WdSyQCN+QifU6BbxVId8nPLwoLklWzRAdkTfZcpNmcN0Fs27tkEUbF7wwQLy/3G3iiOj3c Pq5VY5Y5hu9/S1stPG35lljaLoGaDTQv7lstvUoV7pppjxZjl7qIeQLq5S0IVBJpMsPiye QuY4zyH5OINwSb5HwR6kDT+4PJMaty8= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=none; spf=pass (imf20.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com 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 04441DA7; Tue, 30 Jan 2024 00:32:47 -0800 (PST) Received: from [10.57.79.54] (unknown [10.57.79.54]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 4DEEE3F738; Tue, 30 Jan 2024 00:32:00 -0800 (PST) Message-ID: <40cfb242-ceb0-44c6-afe7-c1744825dc62@arm.com> Date: Tue, 30 Jan 2024 08:31:58 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v1 3/9] mm/memory: further separate anon and pagecache folio handling in zap_present_pte() Content-Language: en-GB To: David Hildenbrand , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Matthew Wilcox , Catalin Marinas , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Peter Zijlstra , Michael Ellerman , Christophe Leroy , "Naveen N. Rao" , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Christian Borntraeger , Sven Schnelle , Arnd Bergmann , linux-arch@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org References: <20240129143221.263763-1-david@redhat.com> <20240129143221.263763-4-david@redhat.com> From: Ryan Roberts In-Reply-To: <20240129143221.263763-4-david@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 902151C0021 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: qeheh4oaf91ucwoxygxhcnptfxaabbh7 X-HE-Tag: 1706603524-112293 X-HE-Meta: U2FsdGVkX1+41sq5Ck1lv4g62OsG6s0MfUUifXhzfou3xv7qGGNH14RFB40/oLPFzDSKscVWP/bYqrd9vTewt0rlG7KnnuHRq5X6u17NIS++6mqrCBkSp1Ceq1B2ETkRkzGgGh4m56jeIp2GtODc8zDYtsCefZu6perRb1f2iie4JQJmYuTKi7prytBiL4bZN3Ih24jRDIJjOwTjS9BB9e6uVpvZaSLW0UNEnUhwu/GN9kDDKQiWh8WZHsu/w4GBJw5ozaUp6S7rvhMr4DbBnRLVKSDLzHQskP4alYdmschsVAOo9CBThxUjYuXPXwROAR+A+ye/jM8Tnac3inQ/+AdKaO7oGGllKZBMu9t6qnu1E6i316rus0zi4v+2xGVFiny22eHMav9ng1w8tFa1OX5kijauP09sGTCiJlN+FOg0AQF4Xzq3fNAwr0VcnQSTj6EA/DIo5NI/KvHY3APxdKSx/uk0ZIG8epy+MV2ixiwu9gHBk1LimxPrH/dcHohCxfbGvd9xP2StfmbgYfanbN7XPcDlRQ9dCLRVOxrcUpCmh3gKCXKxyAsiiDtPQsspafLaD5e6ygC/BGGIqlr6hVximcbtYZzwrg5/3VqdUvkHbBzUDXK/Zrm1o/4pVbHKADO+VC8QKNHZreFcc716QcY79+Lc0BfwcKVXE1BudwBkPB2yfl7huIjTdkrSodpIJ6YOgPXCcILU7QQStrKbyJRO7ALcdlHVrei//UtrcYzVziuoQ/NAfmyzy9cwptVsdDcBfuENifWUrPyfw4gkw1vqofkFgMSqspZ4QZVNAYMtEQrgCOPiu6Ljt0mma0aY7/VBdi1XSUX2bO/1W/kHpYB07pbFhPlya1SpcS2JVE+XWsseuY9z9GL8fdeSqV01cS1vR6isSy4i28inNPr2d1qy3UHSKjsbX8cbRfp74cYIrOAj1QmSIfFoYD63q6WWeUQz534XnIhdx2nOQTl OwXFDrWR TcYGiFNuxJ2rJSTo2dNGLLn3ZnKAhlxjFU5/WKDvNBg/TwtVhu002G7rABgA7aW6xNaa5+d4iIJUXdQDbZ6mcjzdjNnB0TpfOEyeWt3H82MqFk+qRBzaqhPSOEPS6PgrzubRTKVsGhFEWgMqnf06Vn6hKVNEuhJwja+UIWmejpDRBG5wxfPk9j/UGU7BiRXSulYOSl+H+r33enV/m8a0xanVtHg== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 29/01/2024 14:32, David Hildenbrand wrote: > We don't need up-to-date accessed-dirty information for anon folios and can > simply work with the ptent we already have. Also, we know the RSS counter > we want to update. > > We can safely move arch_check_zapped_pte() + tlb_remove_tlb_entry() + > zap_install_uffd_wp_if_needed() after updating the folio and RSS. > > While at it, only call zap_install_uffd_wp_if_needed() if there is even > any chance that pte_install_uffd_wp_if_needed() would do *something*. > That is, just don't bother if uffd-wp does not apply. > > Signed-off-by: David Hildenbrand > --- > mm/memory.c | 16 +++++++++++----- > 1 file changed, 11 insertions(+), 5 deletions(-) > > diff --git a/mm/memory.c b/mm/memory.c > index 69502cdc0a7d..20bc13ab8db2 100644 > --- a/mm/memory.c > +++ b/mm/memory.c > @@ -1552,12 +1552,9 @@ static inline void zap_present_pte(struct mmu_gather *tlb, > folio = page_folio(page); > if (unlikely(!should_zap_folio(details, folio))) > return; > - ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); > - arch_check_zapped_pte(vma, ptent); > - tlb_remove_tlb_entry(tlb, pte, addr); > - zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent); > > if (!folio_test_anon(folio)) { > + ptent = ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); > if (pte_dirty(ptent)) { > folio_mark_dirty(folio); > if (tlb_delay_rmap(tlb)) { > @@ -1567,8 +1564,17 @@ static inline void zap_present_pte(struct mmu_gather *tlb, > } > if (pte_young(ptent) && likely(vma_has_recency(vma))) > folio_mark_accessed(folio); > + rss[mm_counter(folio)]--; > + } else { > + /* We don't need up-to-date accessed/dirty bits. */ > + ptep_get_and_clear_full(mm, addr, pte, tlb->fullmm); > + rss[MM_ANONPAGES]--; > } > - rss[mm_counter(folio)]--; > + arch_check_zapped_pte(vma, ptent); Isn't the x86 (only) implementation of this relying on the dirty bit? So doesn't that imply you still need get_and_clear for anon? (And in hindsight I think that logic would apply to the previous patch too?) Impl: void arch_check_zapped_pte(struct vm_area_struct *vma, pte_t pte) { /* * Hardware before shadow stack can (rarely) set Dirty=1 * on a Write=0 PTE. So the below condition * only indicates a software bug when shadow stack is * supported by the HW. This checking is covered in * pte_shstk(). */ VM_WARN_ON_ONCE(!(vma->vm_flags & VM_SHADOW_STACK) && pte_shstk(pte)); } static inline bool pte_shstk(pte_t pte) { return cpu_feature_enabled(X86_FEATURE_SHSTK) && (pte_flags(pte) & (_PAGE_RW | _PAGE_DIRTY)) == _PAGE_DIRTY; } > + tlb_remove_tlb_entry(tlb, pte, addr); > + if (unlikely(userfaultfd_pte_wp(vma, ptent))) > + zap_install_uffd_wp_if_needed(vma, addr, pte, details, ptent); > + > if (!delay_rmap) { > folio_remove_rmap_pte(folio, page, vma); > if (unlikely(page_mapcount(page) < 0))