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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 Content-Language: en-US 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> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org 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