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(p200300cbc707980059ba10069052fb40.dip0.t-ipconnect.de. [2003:cb:c707:9800:59ba:1006:9052:fb40]) by smtp.gmail.com with ESMTPSA id d22-20020a1c7316000000b003f80946116dsm1356132wmb.45.2023.06.16.00.46.59 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Jun 2023 00:47:00 -0700 (PDT) Message-ID: <0ea4728a-8601-bf75-1921-bcde0818aac3@redhat.com> Date: Fri, 16 Jun 2023 09:46:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.12.0 Subject: Re: [PATCH 1/3] mm/memory_hotplug: Allow an override for the memmap_on_memory param To: Vishal Verma , "Rafael J. Wysocki" , Len Brown , Andrew Morton , Oscar Salvador , Dan Williams , Dave Jiang Cc: linux-acpi@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org, Huang Ying , Dave Hansen References: <20230613-vv-kmem_memmap-v1-0-f6de9c6af2c6@intel.com> <20230613-vv-kmem_memmap-v1-1-f6de9c6af2c6@intel.com> From: David Hildenbrand Organization: Red Hat In-Reply-To: <20230613-vv-kmem_memmap-v1-1-f6de9c6af2c6@intel.com> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: A85B2A0003 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: tct3ea1ef9a3ppsextwefnkf9hb4s1uy X-HE-Tag: 1686901625-266591 X-HE-Meta: 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 PIAHeWbL az0jL/uEjsPDKDPAZErcLjFtB8BHYqQbdTtFwDgGaJlFBwTXFR1EOZQoyKYTSZQ9kW7bK2ywkTZHYjvpHLtpA9v4Bnxp5DCaKNDgrbBRt5Atto0KodfW3mkQZL0fwTPxAZk405CK9dt6tZdW/qpR5hqsijGElO6iZOpVkmuOtRH4LROkuv45ZNeyD6kQH5Czy3YLE0MKHb6T85fMvnSixi5bTKW6JW6lQtosv7vFW66kTYgdH/2cMoNA6yVJs/ZtRbZk1ZKo4h9XbV7qFmKLLQMoACnSZHy/mgjETiM9Xo/6x4Ld6oRRNqJGxrqfHWWrRzWhu/QX5MMYsdhqmU5lbselgCHYfhVmy07pZLjBsM8HcaUGPyVz3R9lA1DCiH3fFXfUN1MS0KjbPp4iai/xzCNJyxjpcARNzgr375Q2qd9AaGxM= 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: On 16.06.23 00:00, Vishal Verma wrote: > For memory hotplug to consider MHP_MEMMAP_ON_MEMORY behavior, the > 'memmap_on_memory' module parameter was a hard requirement. > > In preparation for the dax/kmem driver to use memmap_on_memory > semantics, arrange for the module parameter check to be bypassed via the > appropriate mhp_flag. > > Recall that the kmem driver could contribute huge amounts of hotplugged > memory originating from special purposes devices such as CXL memory > expanders. In some cases memmap_on_memory may be the /only/ way this new > memory can be hotplugged. Hence it makes sense for kmem to have a way to > force memmap_on_memory without depending on a module param, if all the > other conditions for it are met. Just let the admin configure it. After all, an admin is involved in configuring the dax/kmem device to begin with. If add_memory() fails you could give a useful hint to the admin. -- Cheers, David / dhildenb