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 2AFD0E7E0B9 for ; Mon, 9 Feb 2026 09:55:50 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=pWdUhgxDzRV7HRH4oVMdvkDRh1YzEzz4iZb5STB4kZI=; b=a2hus6CtGUc4BaF+qbXIQb45/x iNAPFKVjbMyPxYTypBSE4oQWcwYUOAILD4ta9ajebIaP5i+HU8/RjHu/ng8W/ljID5ey4bfp9jOlD Gyxk2JiuaXmmUWuD+SbqLnQtRXxiL034o8URljx0Xy313/fhArALOvlXJN+utsXC8N48TzRk2kq2O cE6AuJhZs1lWPE5k4/WJoNWSuuy6m5rX4kGhoOJYFQZRvDNRn24iIYBgyuZYxlJhBj2XukHE/Y/Pv 4ZM9Z94EnyEBqY/lcSMo9m3eucgdBV+7RCyVDVYKegH8Rda2V5y+ncBDGZYsnuuQRHOSOIJLf/Kvo Rk0Folcg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1vpNzc-0000000FC5L-0n8k; Mon, 09 Feb 2026 09:55:44 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1vpNza-0000000FC55-1MIn for linux-arm-kernel@lists.infradead.org; Mon, 09 Feb 2026 09:55:42 +0000 Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id BF16260008; Mon, 9 Feb 2026 09:55:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 42CBCC116C6; Mon, 9 Feb 2026 09:55:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1770630941; bh=/zeD3Z28iae7zRiVNaHCzegaAUapv7q/BPbPb39QLDM=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Hp5YLrKCuRwe3favx/ifQ0p0b6aYrjP4n19amuwxse5OmQguLmG0YyNj3EnDwckEH 9gSsvHLNMTyKsKOLr6E5wN0uXlhlukk7/c7an/eOOp5NWFdPwxmLSbUvY0uKBYXBTZ H72u0JBu6aQyLFRN7l5Ep3mhYeZVVKHcKFpMJJh3q4qEU2c4IdRSe22N5szVcld7Vx OTIoSM/6N4MRj2VSA/+zk74U8Vj3sjb6L/+7zb7Gi09a7wChNKpBHLKTdQyMEOassi QjMMp48JEp1KzyUZFDv5/0duWDZGMtj+N8vNh2sNh+HKUvR+TXZWP4YVmpz0v/C26w Re0sRKfsAFAsQ== Message-ID: <16fb7985-ec0f-4b56-91e7-404c5114f899@kernel.org> Date: Mon, 9 Feb 2026 10:55:32 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v5 4/5] arm64: mm: implement the architecture-specific clear_flush_young_ptes() To: Baolin Wang , Chris Mason Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, lorenzo.stoakes@oracle.com, ryan.roberts@arm.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, riel@surriel.com, harry.yoo@oracle.com, jannh@google.com, willy@infradead.org, baohua@kernel.org, dev.jain@arm.com, linux-mm@kvack.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org References: <9d866a2644051e13a41ef4d6ca3909c6e1f9e229.1766631066.git.baolin.wang@linux.alibaba.com> <20260128114936.72280-1-clm@meta.com> <07d55759-a50a-457a-badd-85697174116f@kernel.org> <280ae63e-d66e-438f-8045-6c870420fe76@linux.alibaba.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit 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 2/9/26 10:36, Baolin Wang wrote: > > > On 2/9/26 5:09 PM, David Hildenbrand (Arm) wrote: >> On 1/29/26 02:42, Baolin Wang wrote: >>> >>> >>> >>> Indeed. I previously discussed with Ryan whether using pte_cont() was >>> enough, and we believed that invalid PTEs wouldn’t have the PTE_CONT >>> bit set. But we clearly missed the device-folio cases. Thanks for >>> reporting. >>> >>> Andrew, could you please squash the following fix into this patch? If >>> you prefer a new version, please let me know. Thanks. >> >> Isn't the real problem that we should never ever ever ever, try >> clearing the young bit on a non-present pte? >> >> See damon_ptep_mkold() how that is handled with the flushing/notify. >> >> There needs to be a pte_present() check in the caller. > > The handling of ZONE_DEVICE memory in check_pte() makes me me doubt my > earlier understanding. And I think you are right. > >     } else if (pte_present(ptent)) { >         pfn = pte_pfn(ptent); >     } else { >         const softleaf_t entry = softleaf_from_pte(ptent); > >         /* Handle un-addressable ZONE_DEVICE memory */ >         if (!softleaf_is_device_private(entry) && >             !softleaf_is_device_exclusive(entry)) >             return false; > >         pfn = softleaf_to_pfn(entry); >     } > > >> BUT >> >> I recall that folio_referenced() should never apply to ZONE_DEVICE >> folios. folio_referenced() is only called from memory reclaim code, >> and ZONE_DEVICE pages never get reclaimed through vmscan.c > > Thanks for clarifying. So I can drop the pte valid check. We should probably add a safety check in folio_referenced(), warning if we would ever get a ZONE_DEVICE folio passed. Can someone look into that ? :) -- Cheers, David