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[96.255.20.138]) by smtp.gmail.com with ESMTPSA id af79cd13be357-8cfc2cd6ba7sm90953785a.46.2026.03.19.08.14.45 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 19 Mar 2026 08:14:46 -0700 (PDT) Date: Thu, 19 Mar 2026 11:14:44 -0400 From: Gregory Price To: "David Hildenbrand (Arm)" Cc: linux-cxl@vger.kernel.org, dan.j.williams@intel.com, dave.jiang@intel.com, jonathan.cameron@huawei.com, alison.schofield@intel.com, ira.weiny@intel.com, dave@stgolabs.net, linux-kernel@vger.kernel.org, kernel-team@meta.com, vishal.l.verma@intel.com, benjamin.cheatham@amd.com, David Rientjes Subject: Re: cxl/region.c improvements and DAX/Hotplug plumbing Message-ID: References: <4d66eac3-1a2b-4d9d-8a9a-529a19758439@kernel.org> <217b154d-e4d1-4824-b2e3-fea82bc44402@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <217b154d-e4d1-4824-b2e3-fea82bc44402@kernel.org> On Wed, Mar 18, 2026 at 09:53:05AM +0100, David Hildenbrand (Arm) wrote: > > and would change the sysfs pattern to > > echo regionN > cxl/decoder0.0/create_ram_region > > echo regionN > cxl/drivers/sysram_region/bind > > echo online_movable > cxl/devices/dax_regionN/hotplug > > echo dax_regionN > cxl/drivers/dax_region/bind > > > > and gives the user a chance to configure a policy before the region > > is pumped all the way through to the endpoint dax driver. > > Would that still be backwards-compatible? > I've since squared this away with the CXL groups, the answer is a different probe path and leaving the auto-probe logic alone. I still need to re-submit the /hotplug extensions here as an improvement because its useful - but i've cleaned it up considerably to avoid the cross-subsystem nonsense. > > > > For most use-cases yes. For something like FAMFS (distributed shared > > memory), one system onlining a block as kmem could be potentially > > destructive to an entirely separate physical server. > > Right. But shouldn't we fail this already at the add_memory() stage? > Sounds like during onlining is a bit too late. Conceptually, the hotplug > as sysram was already wrong for famfs, or am I wrong? > Mostly this describes the baggage associated with auto-hotplug path for all CXL memory, and the fact that we only have a global-scope auto MHP tag. I've come around to better solutions to this problem. Thanks for the read n_n ~Gregory