From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1793260969; b=gIF+kCbPy5zPXnABFWGpUYCfdSB+4jlkpNkw2AKJgfqik6YLUGex7QVq8gOqzPPadNlZ xeTntIhw2cu28wpUw3HhdSWMQM4e4MvG/LGxyaVW9dV/w6WML2A/fziioquOUGm1x4VYG tGEq6P4sbPuIMQgAlHLdaLn2FJ1S8vo9ARnbAzIj2NFIGuhRRHvw/0mXL1RrZq0V8kuu7 sFJwTwzLUwtYZlaXLH3esoaY8Xyhitm1Hfy9OT1TSX+M5H8bIybS1waKIn35SSsXonZyY BRbUxURF9TKRkP80Hfgsm30IIj41briBLCl+2UFXXFgvkuc8+lWoquonxi/vQE2dChQ== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1793260969; h=DMARC-Filter:Received:Received:DKIM-Signature:Message-ID:Date: MIME-Version:User-Agent:Subject:To:Cc:References:Content-Language: From:In-Reply-To:Content-Type:Content-Transfer-Encoding; bh=k8apCcAMk8pZRsZxsH16Lc+5TIn4jIu/b15pYO6Z0Bs=; b=kozNmppJynsFZqDjh5MZ8SaMW1z12kykwK4Sebl6QafOXOdRhg9JpfLQ5KjXYzTmN2KN FFnjBjXyRQUVXcE4LMQDxYLBkwGBZI8GN6YtpqdqeXl5hFMwJFy+jkUA99Wqsk6trHB6M hFPdnj0auKTNXfkxOJgLaijvtrQ41OIoET5U+5tN4hKXa9FIWu3ikRpTq6RBiaNXh+YVD 8YKQqO7oVh8l5iVTrkDL3LfoRqwoQ8XvIFuP9HkkGewaXZ0eEvKCq5Zy46uIf3PRpADap ogYtv/IJq/EL7yz+7HZU0cZ0+8AyePJ2uY7QtYJIuoRZDUr6e7EKCPnSR8KxkvXzaBA== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass header.d=arm.com header.i=@arm.com header.a=rsa-sha256 header.s=foss header.b=iEbujbYC; arc=none smtp.remote-ip=217.140.110.172 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 72E6F606A31A; Thu, 29 Oct 2026 08:02:48 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.2 smtp.subspace.kernel.org 72E6F606A31A Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com 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=iEbujbYC 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 30B0F15A1; Thu, 29 Oct 2026 01:02:44 -0700 (PDT) Received: from [10.163.164.4] (unknown [10.163.164.4]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 385A33F7B4; Thu, 29 Oct 2026 01:02:26 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1793260967; bh=ef9Fg1J+efa9K0lYaHXATY0/T5dH7yrFdYQc0z2MAV0=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=iEbujbYCswZ8RFK2+bOqH9GrXNfdspdEyeLWvgWq16i/7q0yxHJyjSKh5wRDFg8sA 90j56I5hjCTLgfRploz8x7UQzuMKPs6udMHmkEokQ81ilxBQr2532zpMPLliV7ataQ ekLC1vjHF7zTz0euRAfdkqhMPZF/1uaGmanjmQX8= Message-ID: <720a50ae-5828-450f-a7ee-a7107b884225@arm.com> Date: Thu, 29 Oct 2026 13:32:23 +0530 X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 29/46] mm/mremap: use pudp_huge_get_and_clear() when moving huge PUDs To: "David Hildenbrand (Arm)" , Andrew Morton , Johannes Weiner , Michal Hocko , Qi Zheng , Shakeel Butt , Lorenzo Stoakes , Kairui Song , Barry Song , Axel Rasmussen , Yuanchu Xie , Wei Xu , Baoquan He , Baolin Wang , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Kees Cook , Peter Zijlstra , Jann Horn , Pedro Falcato , Hugh Dickins , Pasha Tatashin , Pratyush Yadav , "Matthew Wilcox (Oracle)" , Jan Kara , Zi Yan , Lance Yang , Rik van Riel , Harry Yoo , Alistair Popple , Nico Pache , Ryan Roberts , Usama Arif , Kiryl Shutsemau , Matthew Brost , John Hubbard , Peter Xu , Will Deacon , "Aneesh Kumar K.V" , Nick Piggin , Oscar Salvador , Minchan Kim , Muchun Song , Xu Xin , Chengming Zhou , Chris Li , Kemeng Shi , Nhat Pham , Youngjun Park , Gregory Price , Joshua Hahn , Rakie Kim , Ying Huang , Jason Gunthorpe Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-cxl@vger.kernel.org, stable@vger.kernel.org References: <20261027-fixes_core-v1-0-6f74bec9a5bb@kernel.org> <20261027-fixes_core-v1-29-6f74bec9a5bb@kernel.org> Content-Language: en-US From: Dev Jain In-Reply-To: <20261027-fixes_core-v1-29-6f74bec9a5bb@kernel.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 27/10/26 4:47 am, David Hildenbrand (Arm) wrote: > move_huge_pud() reads the old PUD and clears it in separate operations. > Hardware accessed or dirty updates between those operations can be lost > when the saved entry is installed at the new address. > > The raw pud_clear() also bypasses page_table_check_pud_clear(), while > set_pud_at() accounts for the destination mapping. This leaves the > checker counts unbalanced for mappings tracked by page table checking. > > To fix it, simply use pudp_huge_get_and_clear(). > > Fixes: 7d846db7d0e2 ("mm/mremap: convert huge PUD move to separate helper") > Cc: stable@vger.kernel.org > Reviewed-by: Lorenzo Stoakes (ARM) > Signed-off-by: David Hildenbrand (Arm) > --- Reviewed-by: Dev Jain > mm/mremap.c | 3 +-- > 1 file changed, 1 insertion(+), 2 deletions(-) > > diff --git a/mm/mremap.c b/mm/mremap.c > index 0d06d7f37f19a..16e736c72d9cb 100644 > --- a/mm/mremap.c > +++ b/mm/mremap.c > @@ -509,8 +509,7 @@ static bool move_huge_pud(struct pagetable_move_control *pmc, > spin_lock_nested(new_ptl, SINGLE_DEPTH_NESTING); > > /* Clear the pud */ > - pud = *old_pud; > - pud_clear(old_pud); > + pud = pudp_huge_get_and_clear(mm, pmc->old_addr, old_pud); > > VM_BUG_ON(!pud_none(*new_pud)); > >