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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8c37f4ccdf8sm1546816385a.23.2026.01.12.06.24.07 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 12 Jan 2026 06:24:08 -0800 (PST) Date: Mon, 12 Jan 2026 09:23:35 -0500 From: Gregory Price To: Hannes Reinecke Cc: "David Hildenbrand (Red Hat)" , linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, osalvador@suse.de, gregkh@linuxfoundation.org, rafael@kernel.org, dakr@kernel.org, akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com Subject: Re: [RFC PATCH] memory,memory_hotplug: allow restricting memory blocks to zone movable Message-ID: References: <9575e042-39f4-4f01-80db-34aaaa9312e6@kernel.org> <616f97b7-24e0-4134-a08d-5abaf07a8b09@kernel.org> <20baab84-c8b0-4c46-a550-21b26b975d07@suse.de> <65c246bc-fb10-4cef-8163-3a55bd96f326@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: C5C0420008 X-Stat-Signature: e9oyguwzawmopk9q195wa36qpdijwgom X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1768227849-817101 X-HE-Meta: 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 xLJGg91W heXaQNrUVp/pB/teuiMZpRA1QBFoXxtp2GatE+jVAiwkT2fd81ywIu0nx4q14fNUFXtjeJZSt2tViEPS6vvc5V5rHBGNyHyaiwP19IghSErvya+SDuPQRiyv/VEY+mYGB0wrKdW3vJOWLO71/DwQC05PvvF98R61VJSC8nvCiK21DyIi6csklKxGy/SGlOPM+jZmLzi54EwVtIpTJARKfYSqkxrdysfKFGrGwhYAqCDosWps92LarVjRp17BJvFfzJohcFR8w/3LQl3srARFvrD5KOjIBrJeSWsdcXZSCezMqQ3neV5cEjZdm5UXbYgJ1FKQAcSx5s7YSDJptynSK8/DPh04FFtq4UE0rDNgl2YyMLA8fTvhAByZXww== 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 Mon, Jan 12, 2026 at 08:28:29AM +0100, Hannes Reinecke wrote: > On 1/9/26 17:41, Gregory Price wrote: > > On Thu, Jan 08, 2026 at 03:16:24PM +0100, David Hildenbrand (Red Hat) wrote: > > > On 1/8/26 08:31, Hannes Reinecke wrote: > > > > On 1/6/26 21:22, David Hildenbrand (Red Hat) wrote: > > > > > On 1/6/26 20:59, Gregory Price wrote: > > > > > > > I'm starting to think this issue is actually the result of bad patterns > > in the cxl driver - namely using dax as a path to hotplug sysram. > > > > I suppose either we need a `cxl/dax_region/remove` that handles the > > whole operation in one go, or > > > > we want `cxl/region/commit` to handle hot(un)plug as a single action. > > > > tl;dr: Split the dax use case from the sysram use case, and make a > > cxl sysram driver directly manage hotplug rather than use dax. > > > > Well ... not sure. > We are doing fine even currently during boot up; we can align policies > and everything to ensure the system comes up with the 'correct' setting > Things start to get iffy if one is reconfiguring memory to move from > daxdev to system ram and vice versa. Hang tight, i'll post an RFC this morning that shows the idea in code. region0/memctl/hotplug - if not already hotplugged, creates the memory blocks unless MHP auto-online or new build config set, do not auto-online region0/memctl/hotunplug - remove memory and hotunplug the blocks Done in a single action region0/memctl/state - accepts [online, online_normal, offline] does the action on the entire memory region under the hotplug lock online - ZONE_MOVABLE online_normal - ZONE_NORMAL I also added the memory event callback to prevent someone from onlining in zone normal if the last online action was 'online'. I've tested this on QEMU and it works fine. ~Gregory