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b=iXvK1xwQeG/DeqCC1tllTKg2SB9yf/3QZ3iJ8CwZx801jmHoZRjFWyoiNwt+tif7e fmETAG9YKLrN+BlA5jdt1RyYSy5Rmts9v3yKep8aE/P6uwiQEY0HAXs3r5k5xTWxAd cnmvU+1CwucMHtSK3poz4hZBj7gonlC/64awt2wBvWiaHXr0a7JZig/3TBXwWg4KzI 5bLf0rpPQpfw6TIFklfjqCsRYVjMeFJsXoeRwAlqcWw5YdloE+jilpnEMbrP51CDeT b3zAlRPQHreaJSFk8BC9UOAmJTM0R1pbmeiiSrZRh6GEp7rnNy/BCU2YepJCXpFcnH GdukEOQ7ZKkAw== Message-ID: <06bcee07-5e56-4a82-95ff-2a8e75b7154d@kernel.org> Date: Tue, 9 Jun 2026 20:22:20 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v4 8/9] dax/kmem: add sysfs interface for atomic hotplug To: Gregory Price Cc: linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-kernel@vger.kernel.org, kernel-team@meta.com, linux-cxl@vger.kernel.org, linux-kselftest@vger.kernel.org, djbw@kernel.org, vishal.l.verma@intel.com, dave.jiang@intel.com, akpm@linux-foundation.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, osalvador@suse.de, shuah@kernel.org, alison.schofield@intel.com, Smita.KoralahalliChannabasappa@amd.com, ira.weiny@intel.com, apopple@nvidia.com, Hannes Reinecke References: <20260605211911.2160954-1-gourry@gourry.net> <20260605211911.2160954-9-gourry@gourry.net> <1cb0514b-c753-411e-8ff8-80fa29837441@kernel.org> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: C832B1A000E X-Stat-Signature: e8yfaej5hyszm516szaezw4diaagsny9 X-Rspam-User: X-HE-Tag: 1781029348-647770 X-HE-Meta: U2FsdGVkX18DZ0Uxk77sehTaW3J41YAHYQZZEjoqLzBs58sBlh5pzR1ke7RqGofivabPdW8O/g5+KnfBOe4OEUWEEydFfJ1lSIMX/nWUC6pLnIDnNfuY4yy91GJJqS4m+yzD+EOTwEs+4n9Tnqz7xhevOqTb+B6I8noGi6mn/WO1TuAOg39OBqzWa8t+chXkSB9pOn8nmCfnLfkOy3sPJpix0s2DfzriuzvnSQjQ6apggjcI7wOt6Ev+bMkmN7FIfA/xj/UvywbRUKyLaleiR4z5AGLl3wXpHaLq2KGp08nTti/A2GqW7HDtlw0OliN+ZJymDnKy/2aTlm3Eo4KJ70vVwBBn72bTjEfAuzYvAQFBZbTlV7/EKAZWH8e1GGLUgG4w46SoVhAvvPLm1Ullz1gb5CYUnpWnog+WUvlT3N23mAUPTl+pzV7/ZZ5tJsVHJsOFdwq6x447rfe15E3g8KpGDpDXBrMybH6OLTocckB8DBMFG8YNEPkqu/lFK+xpECZ8tlcLugVYBWpSBV8hiwqkwf5qeNuTELAOlxMm6yKXsrfEZ5+KMVEdGns/D83Jx/4belVRbHPHFl1wGTxelvwCUuDHoaCtGzZ8rnjj7WWpbSkvDwDMATB6do4bLBWmAqJQfczGGdGdxTS/d0/QM/vYjqgoObbtwYz0gEkFUEJ+ghUChrqfxErRfXQAoZcT+sX2vmUBSEIDwy78ikqIs5fF2Ud+v7C93tApqTunlg3+ADALSS2KJsjj1zSbCoPw7KDvWMxUl4LKsIqvOGr7GoxdBXjm0UzqSi835JZk5Q/XQ00ZZxbWduPiqNE2eBa35HnsEr8ggHzsb94YIVyGd8m9TlzJaVjUcpjpCb16fcnYd06h+Jnw9OrWpzS9n+DysKiEbUPMqrzNDVzjai8zf7RnLpBYR8svznwZz0qokEhhaAp2rkwBUpdmM2wRj/LijIJ3LT8gRZws9zwFuH5 jwEUs4ml CpsiKYlXpL1guAGy6Ar1o5MYaWBWEUiZKSKYjX3ipQTMA0Poj+xUBsKxqjCNXm3xaAnjF0odn4kVmEtvQ8uwEULH+aclu8S4bcHLMEX0MH284DYEZMfQ3qoXSwfsM6Y9SrQUfQAQA5s8kYJF1XM3Z/yHx+OH6xlC4Xs9vUFXOE+x/dWDe5fXKlmxMAelgEVz8p3Tpnsl9sRmVUMXcPybDtuNCryS/10Z8U9DJ89GkNspCUC7v+YbPvN0LvzkdTEJ5uN7X Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/9/26 20:19, Gregory Price wrote: > On Tue, Jun 09, 2026 at 08:11:42PM +0200, David Hildenbrand (Arm) wrote: >> On 6/9/26 17:35, Gregory Price wrote: >>> >>> In patch 6 response i point out adding MMOP_UNPLUGGED >>> >>> If we add MMOP_UNPLUGGED as a state that is only use by callers of >>> memory hotplug to represent the current state - but not as a valid input >>> to memory_hotplug.c - then we can simply this as you request. >>> >>> Although we'll need to add a couple lines to memoryN/state parsing code >>> to disallow MMOP_UNPLUGGED as a valid input (otherwise you could >>> permanently unplug memory without the ability to get it back... unless >>> you want that? Seems useless to me.) >> >> I would just special-case your KMEM-special value, and then branch off to the >> core helpers? >> >> static int dax_kmem_parse_state(const char *buf) >> { >> if (sysfs_streq(buf, "unplugged")) >> return DAX_KMEM_UNPLUGGED; >> return mhp_online_type_from_str(...); >> } >> >> So there is no need to add a value to MM core? >> > > Was going to propose this, but then I thought... well if CXL detactes > itself from dax and does this same pattern, maybe MMOP_UNPLUGGED makes > sense. > > But i'll leave that for another day and do as you suggest. Let me sleep over it :) -- Cheers, David