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 B567BC47DA9 for ; Tue, 30 Jan 2024 08:45:51 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 36E196B009B; Tue, 30 Jan 2024 03:45:51 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 31E876B00A1; Tue, 30 Jan 2024 03:45:51 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 1BF656B00A2; Tue, 30 Jan 2024 03:45:51 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id 082EE6B009B for ; Tue, 30 Jan 2024 03:45:51 -0500 (EST) Received: from smtpin22.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay05.hostedemail.com (Postfix) with ESMTP id C495440234 for ; Tue, 30 Jan 2024 08:45:50 +0000 (UTC) X-FDA: 81735344460.22.E5DE9DB Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf27.hostedemail.com (Postfix) with ESMTP id 74B2E4000F for ; Tue, 30 Jan 2024 08:45:48 +0000 (UTC) Authentication-Results: imf27.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf27.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1706604348; 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=Ks2+JNJg1ArNLj0KToMmFpPYxWEEQ0PiogT9em1TKh0=; b=7yzjsSMWT+ngCAIGpw0ewyWhwwog9iO0K90PWtgepyWx/Y3FmuOQvSYH6ywN/hyyBreBTS BTG5xooq03/vYOgZkrEW59slmytYPq/tTJQM0rV2VSjPMF7nnAlCQnoqnSHu8MQmSTDGLS LWYKjeZWnBR0zA+9QbgQ0rqqZOTUiYE= ARC-Authentication-Results: i=1; imf27.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf27.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1706604348; a=rsa-sha256; cv=none; b=8qqslyGzNphKTTy6lC2UK/1BlFXvpBc/SDkhn3FMlXV735PYm92rM1GBKTnkbWUdzTSxrI zhzhT0WT7c1jBqrPt79NKtwimdm2rzo0rXd5m/WyZDo5jDbIzu6+xrMOqd6b6J7PI6uPz+ oq/PWBkcjqcrXqxcKA9VEQvTV6jUP30= 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 600E3DA7; Tue, 30 Jan 2024 00:46:31 -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 8B93E3F738; Tue, 30 Jan 2024 00:45:43 -0800 (PST) Message-ID: Date: Tue, 30 Jan 2024 08:45:41 +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> <40cfb242-ceb0-44c6-afe7-c1744825dc62@arm.com> From: Ryan Roberts In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 74B2E4000F X-Stat-Signature: h6yjzmygwsauycg1ksfsozk8ietkos88 X-Rspam-User: X-HE-Tag: 1706604348-817803 X-HE-Meta: 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 sdTZczvP xbh2OIQnpiY0/MXeCPyeURRZqHR9NiY/WSdcRlrGKEcMvq1eTGwfom565TgudvxcZmngtW2YKp0b/oE/9QIj4sTKl5L9wiz4O5D3wjLXpOZqf/QMdY1NbtDIY6quHeNi1gq73lKVSRehpp6GceKo1BL1HPmL6eSVThRIFBi4Glxno9ZSnzcqDNFb4AM35/BLJgYWw9TiRvJaYfIOWJWgcdvtxij21csZ03vE/56hgGSVUPEjARc8Xm0lFXZrZcRKtY/5cxr74+SQQXWRQ1d27/CpexhwuchwSPArgE+slZKKkSOkvgGSj5sX8sg== 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 30/01/2024 08:37, David Hildenbrand wrote: > On 30.01.24 09:31, Ryan Roberts wrote: >> 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?) > > x86 uses the encoding !writable && dirty to indicate special shadow stacks. That > is, the hw dirty bit is set by software (to create that combination), not by > hardware. > > So you don't have to sync against any hw changes of the hw dirty bit. What you > had in the original PTE you read is sufficient. > Right, got it. In that case: Reviewed-by: Ryan Roberts