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Fri, 6 Feb 2026 16:26:45 +0000 Date: Fri, 6 Feb 2026 16:26:44 +0000 From: Jonathan Cameron To: Gregory Price CC: Andrew Morton , Cui Chao , , Mike Rapoport , Wang Yinfeng , , , , , "David Hildenbrand (Arm)" Subject: Re: [PATCH v2 1/1] mm: numa_memblks: Identify the accurate NUMA ID of CFMW Message-ID: <20260206162644.000050fe@huawei.com> In-Reply-To: References: <20260115101858.85fd7b8e837c1c92a4fdc5f0@linux-foundation.org> <696944eca1837_34d2a10056@dwillia2-mobl4.notmuch> <2d1e23ad-7ec1-483b-88b3-70ce19b69106@phytium.com.cn> <20260205145842.efb90572a902ae4c481e6ef6@linux-foundation.org> <20260206110305.00001fbb@huawei.com> <20260206150941.000028ae@huawei.com> X-Mailer: Claws Mail 4.3.0 (GTK 3.24.42; x86_64-w64-mingw32) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.203.177.15] X-ClientProxiedBy: lhrpeml100010.china.huawei.com (7.191.174.197) To dubpeml500005.china.huawei.com (7.214.145.207) X-Rspamd-Queue-Id: 791B740013 X-Stat-Signature: hnfajewitpin7i8umn4w1yreqw5q51r4 X-Rspam-User: X-Rspamd-Server: rspam02 X-HE-Tag: 1770395208-777735 X-HE-Meta: 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 2zlWwWF4 DJlZFn7KZNLxhOjeWaLYrw4U2Y7SrZ2YpC0VigDM8OYQcWv8/WIcL+tWX542k55p170QhYlOVkH06DTW4deGEbtJjmr8kV4VBUVWGZChUnrUfFDX+BWekQoXhZx4R0YRAeGkQ9XdLV/zi5JMBdXp0EpGXnDKbCCW8OAwZr8PDtV21/RFKDl04A5glJdo+ZHlTbkryK530EcXRc6NPzs6XOldRz6v3V5rmQsNOJssMnnPy9zxR23uzGiltdIpw9NyQFbluDn70Gdc9Pav4fcyavONxncc3DFc3oAjHHrGBtPiNCul8w+d9+2BE8u+LS/+2m6ZQR9ws3P84sJs= 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 Fri, 6 Feb 2026 10:53:11 -0500 Gregory Price wrote: > On Fri, Feb 06, 2026 at 03:09:41PM +0000, Jonathan Cameron wrote: > > On Fri, 6 Feb 2026 08:31:09 -0500 > > Gregory Price wrote: > > > > Now a fun corner is that a node isn't created unless there is something > > in it - the whole SRAT is the source of truth for what nodes exist > > - so we need 'something' in it - a cpu will do, or a GI, probably a GP. > > Otherwise memory ends up in node0. However, fallback lists etc happen > > as normal when first mem in a node is added. > > > ... > > For now I 'suspect' we could hack things to provide lots of waiting numa nodes > > and merrily assign HPA into them as we like whatever SRAT provides > > in the way of 'hints' :) > > > > look at ACPI MSCT - "Maximum Proximity Domain Information Structure" ;] > > I don't remember reading anything in the ACPI spec that says something > has to be ON any of these PXMs for it to be accounted for in the MSCT. > > Platforms can just say "Reserve that many Nodes". > > (Linux does not read this value, and on my existing systems, this number > always reflects the number of actually present PXMs) > > --- > > We probably want to ignore that and just add this: > > CONFIG_ACPI_NUMA_NODES_PER_CFMWS > int > range 1 4 > help > This option determines the number of NUMA nodes that will be > added for each CEDT CFMWS entry. > > By default ACPI reserves 1 per unique PXM entry in the SRAT, > or 1 for a CXL Fixed Memory Window without SRAT mappings. > > This will reserve up to N nodes per CEDT entry, even if that > CEDT has one or more SRAT entries. > > then in the acpi/numa/srat.c code that parses srat/cedt, just track > the number of nodes over a CEDT range. > > for each srat: > account_unique_pxm(pxm, srat_range) > > for each cedt: > nr_nodes = unique_pxms(cedt_range) > while (nr_nodes < CONFIG_ACPI_NUMA_NODES_PER_CFMWS) > node = acpi_map_pxm_to_node(*fake_pxm++); > if (node == NUMA_NO_NODE): > err("Unable to reserve additional nodes for CXL windows") > break; > node_set(node, numa_nodes_parsed); > nr_nodes++ > > This should fall out cleanly. > > The additional nodes won't be associated with anything, but could be > used for hotplug - I imagine. > That aligns with what I was thinking as a first solution to allowing this to be more dynamic. We can get clever later if this doesn't prove sufficient. Jonathan > ~Gregory