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 0DC96C48BF3 for ; Fri, 16 Feb 2024 12:35:17 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 997D76B0071; Fri, 16 Feb 2024 07:35:16 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 921D46B00A5; Fri, 16 Feb 2024 07:35:16 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 7E9A76B0081; Fri, 16 Feb 2024 07:35:16 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0015.hostedemail.com [216.40.44.15]) by kanga.kvack.org (Postfix) with ESMTP id 696148D0006 for ; Fri, 16 Feb 2024 07:35:16 -0500 (EST) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id 4B1811C015F for ; Fri, 16 Feb 2024 12:35:16 +0000 (UTC) X-FDA: 81797612232.06.0805A21 Received: from sin.source.kernel.org (sin.source.kernel.org [145.40.73.55]) by imf19.hostedemail.com (Postfix) with ESMTP id 57E9C1A001B for ; Fri, 16 Feb 2024 12:35:13 +0000 (UTC) Authentication-Results: imf19.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf19.hostedemail.com: domain of cmarinas@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1708086914; 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: in-reply-to:in-reply-to:references:references; bh=cNtECzRiDhUsTEdoCNh/dOrnaW6vsuUNvcbYAJRTRNo=; b=e9oOtx9JYbEDwsGNVCwqV2aGMo2GDUmDQgAL5X8XKfVw5hMIQLgs/kBh8Sarver+SwoN4k bWE6lZwJmNxKtNgdGE06ZkG72P2NyAV01Q0ApacsYt4965gGhuAskqZuOaBx1LMIoXnIQM aTcseR5g6FkYT95tQnA91dOcp18LdeU= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=none; dmarc=fail reason="SPF not aligned (relaxed), No valid DKIM" header.from=arm.com (policy=none); spf=pass (imf19.hostedemail.com: domain of cmarinas@kernel.org designates 145.40.73.55 as permitted sender) smtp.mailfrom=cmarinas@kernel.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1708086914; a=rsa-sha256; cv=none; b=a7ZWuLTs+HTP5BfgPldLKNONt0yICtUDKBcQgBEyWGmXP6t4rPcTWBKDarvZCis4f2Ag/q JhosHBnIiuFc4iRG/ZEOG3+YKmGxJs4iXi3gfRuygAEqBAU7LWeRf9sBuICtVY0+kuZfIE nMqS5IMIcK5eWWS5+7VD1Io2eIM8RbU= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sin.source.kernel.org (Postfix) with ESMTP id 0D6E5CE2B32; Fri, 16 Feb 2024 12:35:11 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 26F79C43394; Fri, 16 Feb 2024 12:35:05 +0000 (UTC) Date: Fri, 16 Feb 2024 12:35:03 +0000 From: Catalin Marinas To: Ryan Roberts Cc: Will Deacon , Ard Biesheuvel , Marc Zyngier , James Morse , Andrey Ryabinin , Andrew Morton , Matthew Wilcox , Mark Rutland , David Hildenbrand , Kefeng Wang , John Hubbard , Zi Yan , Barry Song <21cnbao@gmail.com>, Alistair Popple , Yang Shi , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , "H. Peter Anvin" , linux-arm-kernel@lists.infradead.org, x86@kernel.org, linuxppc-dev@lists.ozlabs.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v6 18/18] arm64/mm: Automatically fold contpte mappings Message-ID: References: <20240215103205.2607016-1-ryan.roberts@arm.com> <20240215103205.2607016-19-ryan.roberts@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240215103205.2607016-19-ryan.roberts@arm.com> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 57E9C1A001B X-Stat-Signature: jpj6naphd65ogjx94a6m4bpjbjyhfoqj X-Rspam-User: X-HE-Tag: 1708086913-248796 X-HE-Meta: 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 DZZWr5hP d5DDwg+xBzrRWNLZprYvjlD8vja9h9vkOSBbW0/LviVGlveEk571RtvroWWVsrUaLcb7VOrsi7BpprgDpZczXu0OdNtjKC7ZzLboO6Drc2A+lSj4= 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 Thu, Feb 15, 2024 at 10:32:05AM +0000, Ryan Roberts wrote: > There are situations where a change to a single PTE could cause the > contpte block in which it resides to become foldable (i.e. could be > repainted with the contiguous bit). Such situations arise, for example, > when user space temporarily changes protections, via mprotect, for > individual pages, such can be the case for certain garbage collectors. > > We would like to detect when such a PTE change occurs. However this can > be expensive due to the amount of checking required. Therefore only > perform the checks when an indiviual PTE is modified via mprotect > (ptep_modify_prot_commit() -> set_pte_at() -> set_ptes(nr=1)) and only > when we are setting the final PTE in a contpte-aligned block. > > Signed-off-by: Ryan Roberts Acked-by: Catalin Marinas