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Wysocki" , Robert Moore , Bjorn Helgaas , "Rafael J. Wysocki" Subject: Re: [PATCH v4 3/3] PCI/ACPI: negotiate CXL _OSC Message-ID: <20220401204014.khgozoeu6biirknu@offworld> References: <20220331202022.1823174-1-vishal.l.verma@intel.com> <20220331202022.1823174-4-vishal.l.verma@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Disposition: inline In-Reply-To: <20220331202022.1823174-4-vishal.l.verma@intel.com> User-Agent: NeoMutt/20201120 Precedence: bulk List-ID: X-Mailing-List: linux-acpi@vger.kernel.org On Thu, 31 Mar 2022, Vishal Verma wrote: >The CXL specification does not define any additional constraints on >the hotplug flow beyond PCIe native hotplug, so a kernel that supports >native PCIe hotplug, supports CXL hotplug. Hmm but from a Linux-pov does it make sense to allow hotplug support if the MM cannot handle it? @@ -531,7 +518,8 @@ static u32 calculate_cxl_support(void) support = OSC_CXL_2_0_PORT_DEV_REG_ACCESS_SUPPORT; if (pci_aer_available()) support |= OSC_CXL_PROTOCOL_ERR_REPORTING_SUPPORT; - if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE)) + if (IS_ENABLED(CONFIG_HOTPLUG_PCI_PCIE) && + IS_ENABLED(CONFIG_MEMORY_HOTPLUG)) support |= OSC_CXL_NATIVE_HP_SUPPORT; return support; After all, per the CXL 2.0 Type 3 device Hot-Add flow: "" 7. CXL aware software notifies OS memory manager about the new memory and its attributes such as latency and bandwidth. Memory manager processes a request and adds the new memory to its allocation pool. "" Thanks, Davidlohr