From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.subspace.kernel.org (Postfix) with ESMTP id E70AE606A31F for ; Mon, 26 Oct 2026 12:30:54 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key, unprotected) header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=a51umk1S Received: by kanga.kvack.org (Postfix) id 05C9B6B05B3; Mon, 26 Oct 2026 08:30:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 033F36B05B5; Mon, 26 Oct 2026 08:30:53 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id EB3B36B05B6; Mon, 26 Oct 2026 08:30:53 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0011.hostedemail.com [216.40.44.11]) by kanga.kvack.org (Postfix) with ESMTP id D2FD26B05B3 for ; Mon, 26 Oct 2026 08:30:53 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay04.hostedemail.com (Postfix) with ESMTP id 659811A05E3 for ; Mon, 26 Oct 2026 12:30:53 +0000 (UTC) X-FDA: 85364711586.20.BF4027B Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by imf18.hostedemail.com (Postfix) with ESMTP id 5D7FD1C000A for ; Mon, 26 Oct 2026 12:30:51 +0000 (UTC) Authentication-Results: imf18.hostedemail.com; dkim=pass header.d=arm.com header.s=foss header.b=a51umk1S; spf=pass (imf18.hostedemail.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=catalin.marinas@arm.com; dmarc=pass (policy=none) header.from=arm.com ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1793017851; b=E7bduqtlp3rH8HcL18d5qioupm9DoNyl9zNoECpp0j3ZdC7+q6lvp1GkpBdw9YwjcKBlVK DwqUEPNZ56gzARQTWF4mZWrAD/xHstwhXnx/9XizqiaVLBpGAPBsmBR6gM+EsecdB73RM+ xt+0ywTUj3kW9x68zJz+AaoMxKwUAGQ= ARC-Authentication-Results: i=1; imf18.hostedemail.com; dkim=pass header.d=arm.com header.s=foss header.b=a51umk1S; spf=pass (imf18.hostedemail.com: domain of catalin.marinas@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=catalin.marinas@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=1793017851; 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:dkim-signature; bh=TRZt7x37p8LUgQOIpKaz3b3988dBzwRGltnd5ZVeEBQ=; b=xBgFLOF1JZ65+X5HZoxdvt1rW7XLwowGnVtQrKJGZjVY/vSDRYEF3372o0zTN+W3E0brl1 iaO3tv6iVlv0WHYKjlNyGi2N0DlrhluRb0vsg6xFXU87iz2gNgpZI7XN0BPYlMyPy0b0Wi pqDgu80BhS9mzeMapRh+y2SVJJzKn8M= 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 2F3F025DF; Mon, 26 Oct 2026 05:30:47 -0700 (PDT) Received: from arm.com (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 16F583F7B4; Mon, 26 Oct 2026 05:30:47 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793017850; bh=X7sXgG5KeOSy1aHvYxzPYxQhid9EVso1C+EnXtpcXiA=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a51umk1SJn3Qg0uasCVQzZnOrDFKghUAEP7EkrWFXdPPNFIMzLLrV9N8cjkr3aGKF z8GG4zNZ3Tm/0q6VoX6Psp3ZxfySUkB3fkJWOhbNWs22m0DRA+otCMqkcURphbPTl5 fFeWa3OFzRFlj5VqI9kqkZNToJ4SuBOlO68fncXY= Date: Mon, 26 Oct 2026 12:30:45 +0000 From: Catalin Marinas To: Zhao Gongyi Cc: "David Hildenbrand (Arm)" , will@kernel.org, Ryan Roberts , dev.jain@arm.com, baolin.wang@linux.alibaba.com, lance.yang@linux.dev, mark.rutland@arm.com, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, stable@vger.kernel.org Subject: Re: [PATCH] arm64/mm: restrict transparent contpte mappings to valid PTEs Message-ID: References: <20261013093600.54995-1-zhaogongyi@bytedance.com> <3b57c214-6a43-4fc7-a531-fb5eac196465@bytedance.com> X-Archived-By: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <3b57c214-6a43-4fc7-a531-fb5eac196465@bytedance.com> X-Stat-Signature: af3agg6dan1znqucpyjnatyacowrrkh3 X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_PASS,SPF_PASS autolearn=no autolearn_force=no version=4.0.1 X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 5D7FD1C000A X-Rspam-User: X-HE-Tag: 1793017851-311014 X-HE-Meta: U2FsdGVkX1+AOctzw2WnFI5g0UNXruN1kY233T4fxSXK1JE/tQhEzwSAhlUygoFXmdyBKEmekb6Tuj+O2gHniSEHIy4HGEq+1XRYLRJM1vQqiYBg/ITf0ODuEV3R7fx0t27WsQHny04zsw07Ouqy7tn/tXPNVuTkMzCLwuKq/L1vqurYSjFhWwlbRr/l5a6Qyc+DGhUvN5V6n2vXwutL+jUlqOEVxF4DCG7c7HLGczyQaBU9RL3OvMoVF7VmJ1UtrGkf2K9dT5T7MM4bZhQbqihOfOVcRdHuXKI6S3TFIqhOTZUxLRKI9eeeLT2LZQ3XdHKij7u8Dl9WjxA7YpJcS/RpS9YHooujubap4PaRH/geg9Y670bP0IpYiaRgGT7OZGhKIRL5LqwuwYLq9JKli4S66BlL3r0Qt7PkQ9Qy80a8IS0xtMkR2E/Xx2eErd28VDUqYy1S2pynk0QV9wn3RocpoUl5fG5CjRgFDH1sIsOuB1Cs8HSMyBDr//w00WryeY/8jURSNAonkzczM78j78TK0XErcN1+fAifMggTnosFq9wrFkAn6rtlJ9zED4vb3ZYZzC+Bt78+Z8Amnshr5qpRkK5CcEteLKAWlR9TsrHAmL/L7GdeinAO0gm4glHYfPkoKzRhV55uTqFAvD8Ag7YuAYyj4MhBs8RC+B0FgzZlZq8uhjNLiq6fna7xIziNmLBaR+6ihqvh8gu2uoTTnTm54Uo1mwbI66RVvF6hCCf9Qdaid4UWw2USCJbjJbkFaGenkYEJpPbw+5ikJJo65so+NqRaE+quJbW9KxuJxLbJ0QjU2uIG3PTn91W4Ba7AgHxBKbM3lEAYOToZ10DaOQOVsFe5U4wSVWzoOEkUA7t/FGQnaQa/EpRFDa3AQuidixI6n+AL6C9OrVhQuudTrAnXffxCsEO5weK3WcpKFk5Lx6bQ9FcSFL+wVhGbhPP1emiSdn8naOP+qF/sstQ RFGUW89w ZU9umTYZ+5RU5Tdd6nqm9rROIy7sg/I6nJXUeZc+1LQcthG+U4yA7gAvMF8xV9MdJ9gfEIPK7tturDRu8yhIVZU+hwN1/uLK+GUQvx3vU5c+SAhv5HcufA8nKBAUJMpQYMN/rqrfNafgsfQo7aBY00SQbi2c7T2T3AicHBA71mM1Lo75P2uGz1lLY8ofNvuqmxd5nfnFrtDpSNM3k53OfGYrnrr8eDsM/VGDnozOlJJBsY3ZxdyPREkSzP55GvbhCkwjvvXK/OFTSaUanNZSvIYFJeO7iFC9amYWPJlOpi5v+msVxNLjeBAhSnQ== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: X-Spam-Checker-Version: SpamAssassin 4.0.1 (2024-03-26) on aws-us-west-2-korg-listserv-alma10-1 On Sun, Oct 25, 2026 at 12:00:33AM +0800, Zhao Gongyi wrote: > On 10/24/26 4:55 AM, David Hildenbrand (Arm) wrote: > > If we have the spare PTE bit, why shouldn't we just use it? > > > > It will make batching over PTEs faster. And we care about that for present PTEs. > > > > So I don't quite see why the stable fix couldn't just do it right away? Do you > > have a prototype that shows that it would require significant code changes? > > I tried a small prototype that keeps PTE_CONT on present-invalid PTEs. > It leaves contpte_set_ptes() unchanged and makes contpte_try_unfold() > recognize pte_present(pte) && pte_cont(pte), instead of checking only > pte_valid_cont(pte). I think it's worth doing but currently not sure it buys us much unless we also change pte_batch_hint() to cover such entries. However, if we do this, we need to audit the other pte_valid_cont() callers (e.g. ptep_get() needs updating as well). So, if we aren't going to change pte_batch_hint() as a backport fix (I don't think we should, it's an optimisation), I'd rather take v2 now and continue with a proper pte_present_cont() etc. patchset on top. -- Catalin