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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 51DD9CAC5A7 for ; Wed, 24 Sep 2025 08:50:18 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=J4cKTSeea7/czdVYO122nuGfInlG59hXiu0r7c4Sres=; b=qbY1WkrQje8t34DcYlXjbOoo4H 5HXVF2OkrojMX2t0mVSvNAbQKG1Zt2MpktkEvo3BH3g9/9YeoT2JgCjE8CTxNMqfrMhvJRYGPp93p 0sbxyF/wHG9VkFeIIgvgMINbpXD7LZLXJnFrkJIVkXjm3EDO0DHu18PtJoEmQswVWeczthB4j2dzC AndglLeC93fivTFGCB4tnswiM/BJ32T2Yy2C73n2DcqDdDYRilSNBPxXqPoRahwdrVOlvbrK9N+uh w2qyUm03zDapkOaFhvr349RCGpOvxStSlhFHzy+3lnoP09BAY4NpAnftR5aSilxfpltTyeJ99SA0C RpQK/5+g==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1v1LCW-0000000FwFY-15LV; Wed, 24 Sep 2025 08:50:12 +0000 Received: from sea.source.kernel.org ([2600:3c0a:e001:78e:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1v1LCT-0000000FwEE-3zBg; Wed, 24 Sep 2025 08:50:11 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by sea.source.kernel.org (Postfix) with ESMTP id 91B4643CCC; Wed, 24 Sep 2025 08:50:09 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id E087DC4CEE7; Wed, 24 Sep 2025 08:50:02 +0000 (UTC) Date: Wed, 24 Sep 2025 09:50:00 +0100 From: Catalin Marinas To: Lance Yang Cc: David Hildenbrand , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, usamaarif642@gmail.com, yuzhao@google.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, baohua@kernel.org, voidice@gmail.com, Liam.Howlett@oracle.com, cerasuolodomenico@gmail.com, hannes@cmpxchg.org, kaleshsingh@google.com, npache@redhat.com, riel@surriel.com, roman.gushchin@linux.dev, rppt@kernel.org, ryan.roberts@arm.com, dev.jain@arm.com, ryncsn@gmail.com, shakeel.butt@linux.dev, surenb@google.com, hughd@google.com, willy@infradead.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, qun-wei.lin@mediatek.com, Andrew.Yang@mediatek.com, casper.li@mediatek.com, chinwen.chang@mediatek.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mediatek@lists.infradead.org, linux-mm@kvack.org, ioworker0@gmail.com, stable@vger.kernel.org Subject: Re: [PATCH 1/1] mm/thp: fix MTE tag mismatch when replacing zero-filled subpages Message-ID: References: <20250922021458.68123-1-lance.yang@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250924_015010_009547_B9C53F51 X-CRM114-Status: GOOD ( 16.99 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Wed, Sep 24, 2025 at 10:49:27AM +0800, Lance Yang wrote: > On 2025/9/24 00:14, Catalin Marinas wrote: > > So alternative patch that also fixes the deferred struct page init (on > > the assumptions that the zero page is always mapped as pte_special(): > > I can confirm that this alternative patch also works correctly; my tests > for MTE all pass ;) Thanks Lance for testing. I'll post one of the variants today. > This looks like a better fix since it solves the boot hang issue too. In principle, yes, until I tracked down why I changed it in the first place - 68d54ceeec0e ("arm64: mte: Allow PTRACE_PEEKMTETAGS access to the zero page"). ptrace() can read tags from PROT_MTE mappings and we want to allow reading zeroes as well if the page points to the zero page. Not flagging the page as PG_mte_tagged caused issues. I can change the logic in the ptrace() code, I just need to figure out what happens to the huge zero page. Ideally we should treat both in the same way but, AFAICT, we don't use pmd_mkspecial() on the huge zero page, so it gets flagged with PG_mte_tagged. If I go with the first fix for the page merging, I'll look to defer the zero page initialisation post page_alloc_init_late() in a separate patch. -- Catalin