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b=M57mQ1lgAvcDoFKMJagLrAPDOPLRGYbL54K0eggKgRhi+HLPrzU/+ou4rdo9OGqeM 1ehjSVG0IY7mMD0hvPbVHFCjQl7f0aVtD6H/W9ELDFzfWT/yyWosIXwgaCmV7X3tEE OkiPvmjt6tir0FKmyOWOYrpazHopBAj2Zc+UEQRg= Date: Thu, 8 Jan 2026 09:48:12 -0800 From: Andrew Morton To: Cui Chao Cc: Jonathan Cameron , Mike Rapoport , Wang Yinfeng , linux-cxl@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH v2 1/1] mm: numa_memblks: Identify the accurate NUMA ID of CFMW Message-Id: <20260108094812.8757ce3ad8370668eaafb29c@linux-foundation.org> In-Reply-To: <20260106031042.1606729-2-cuichao1753@phytium.com.cn> References: <20260106031042.1606729-1-cuichao1753@phytium.com.cn> <20260106031042.1606729-2-cuichao1753@phytium.com.cn> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Stat-Signature: j3unmwk16ippxktwccyfunt5xcfo7aig X-Rspam-User: X-Rspamd-Queue-Id: F172C40003 X-Rspamd-Server: rspam08 X-HE-Tag: 1767894494-868982 X-HE-Meta: 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 LYQs3gT2 6yFLaQI53gp1ZmbybdyKYJCVmQFRMfsULFjSx0ATC4/hBGMFiMj4CmuLM5vPBR8Cd7jNPk9JoW4xiKT3DQ9YqmeQKnO7v2DYkZbtvCarjtefFMT6/4RI48VDgMx7CvKeMy/NLIaIKU5MCHY+RqQI0si8WcO8nRaOQg9mnNJVowwkWuRltgp//Op9ZXbLoj9xgB5UkZZHbunO1/O7mq6++CnoAF66fdK6s/9vDNbbtwJyFo0QGwGqk15ZWI7ILVHR3UbJpMkhqj9lTGrdeSQweTRIK9XX/aIW8lvexTpjtlrR0ioI4fStzQEB3C/6hPEDPn507zHfaB3ig/q6+yBz+In6mqgyWw/6ZfATG 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 Tue, 6 Jan 2026 11:10:42 +0800 Cui Chao wrote: > In some physical memory layout designs, the address space of CFMW > resides between multiple segments of system memory belonging to > the same NUMA node. In numa_cleanup_meminfo, these multiple segments > of system memory are merged into a larger numa_memblk. When > identifying which NUMA node the CFMW belongs to, it may be incorrectly > assigned to the NUMA node of the merged system memory. > > Example memory layout: > > Physical address space: > 0x00000000 - 0x1FFFFFFF System RAM (node0) > 0x20000000 - 0x2FFFFFFF CXL CFMW (node2) > 0x40000000 - 0x5FFFFFFF System RAM (node0) > 0x60000000 - 0x7FFFFFFF System RAM (node1) > > After numa_cleanup_meminfo, the two node0 segments are merged into one: > 0x00000000 - 0x5FFFFFFF System RAM (node0) // CFMW is inside the range > 0x60000000 - 0x7FFFFFFF System RAM (node1) > > So the CFMW (0x20000000-0x2FFFFFFF) will be incorrectly assigned to node0. > > To address this scenario, accurately identifying the correct NUMA node > can be achieved by checking whether the region belongs to both > numa_meminfo and numa_reserved_meminfo. Thanks. Can you please help us understand the userspace-visible runtime effects of this incorrect assignment?