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 A3777C28B30 for ; Mon, 17 Mar 2025 15:31:01 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B8A24280002; Mon, 17 Mar 2025 11:31:00 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B3924280001; Mon, 17 Mar 2025 11:31:00 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id A00C1280002; Mon, 17 Mar 2025 11:31:00 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 83B6B280001 for ; Mon, 17 Mar 2025 11:31:00 -0400 (EDT) Received: from smtpin23.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 6EBEEA5595 for ; Mon, 17 Mar 2025 15:31:00 +0000 (UTC) X-FDA: 83231431080.23.4702CB8 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf12.hostedemail.com (Postfix) with ESMTP id 5E43140029 for ; Mon, 17 Mar 2025 15:30:55 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf12.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=1742225457; a=rsa-sha256; cv=none; b=MsgVrzbDxQASR7gtu9BZQYst1kevsQpe8EmtE4U/iTmgMvF4ikpjTmWhUzcnidEltt8VOY dA1abiSq+EbAPQiHi9+we5ugu1xCNzLdgQ8AO4GVBIPeWi+5NDNj0R1V1GDdVSooZjnJRl 0aJWA5AVPXyphUxNR8tN6PXPePRFTgU= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none; dmarc=pass (policy=none) header.from=arm.com; spf=pass (imf12.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=1742225457; 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=E28zglszNSgNs5nxBqGH9ihoTQywx6FCChBvwXjU3Lc=; b=AZq++1Qzc429e/1+UoOinaO/plCbPJngwkvI1qZoEFS8rg3xiZr/DfxfFsjTrgJO86mYKn BMSrpdiID1cta3K2h3cawPQffFn2kmzY8bKS8WIx/56Rrfn/auAHuBW5qOk07jsTFD0bKo kTbVbFuNNKSJNdn/c/OygfSFaJiYBp8= 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 3164013D5; Mon, 17 Mar 2025 08:31:03 -0700 (PDT) Received: from [10.57.84.137] (unknown [10.57.84.137]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 421503F694; Mon, 17 Mar 2025 08:30:49 -0700 (PDT) Message-ID: <70349335-84ee-4bca-a3d6-d7cf3c05b92b@arm.com> Date: Mon, 17 Mar 2025 15:30:47 +0000 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 00/11] Always call constructor for kernel page tables Content-Language: en-GB To: Kevin Brodsky , linux-mm@kvack.org Cc: linux-kernel@vger.kernel.org, Albert Ou , Andreas Larsson , Andrew Morton , Catalin Marinas , Dave Hansen , "David S. Miller" , Geert Uytterhoeven , Linus Walleij , Madhavan Srinivasan , Mark Rutland , Matthew Wilcox , Michael Ellerman , "Mike Rapoport (IBM)" , Palmer Dabbelt , Paul Walmsley , Peter Zijlstra , Qi Zheng , Will Deacon , Yang Shi , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, sparclinux@vger.kernel.org References: <20250317141700.3701581-1-kevin.brodsky@arm.com> From: Ryan Roberts In-Reply-To: <20250317141700.3701581-1-kevin.brodsky@arm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: ymbcc19t4bynpzp9c3xfxpsuuxsou19w X-Rspamd-Queue-Id: 5E43140029 X-HE-Tag: 1742225455-133231 X-HE-Meta: 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 O0IgarI7 yJ+h/CHUTomuK4ib/tuoDfbnkfFyeXp/ExBZCfNHjoZfA+Tfv0RGJ6w3Z4P+DfWHSAqOf3W7TbwejBByG7KPfEhJbL4LO2vLJjP/IvOudnU1nkScCfRCzujd13OiS4aci0hid8twxCEGsjYMuyf7wXv9fMQ== 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 17/03/2025 14:16, Kevin Brodsky wrote: > The complications in those special pgtable allocators beg the question: > does it really make sense to treat efi_mm and init_mm differently in > e.g. apply_to_pte_range()? Maybe what we really need is a way to tell if > an mm corresponds to user memory or not, and never use split locks for > non-user mm's. Feedback and suggestions welcome! The difference in treatment is whether or not the ptl is taken, right? So the real question is when calling apply_to_pte_range() for efi_mm, is there already a higher level serialization mechanism that prevents racy accesses? For init_mm, I think this is handled implicitly because there is no way for user space to cause apply_to_pte_range() for an arbitrary piece of kernel memory. Although I can't even see where apply_to_page_range() is called for efi_mm. FWIW, contpte.c has mm_is_user() which is used by arm64. Thanks, Ryan