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Fri, 6 Dec 2019 15:46:48 +0000 (UTC) Received: from lacos-laptop-7.usersys.redhat.com (ovpn-116-235.ams2.redhat.com [10.36.116.235]) by smtp.corp.redhat.com (Postfix) with ESMTP id 1050219C7F; Fri, 6 Dec 2019 15:46:42 +0000 (UTC) Subject: Re: [PATCH for-5.0 7/8] acpi: cpuhp: add CPHP_GET_CPU_ID_CMD command To: Igor Mammedov References: <1575479147-6641-1-git-send-email-imammedo@redhat.com> <1575479147-6641-8-git-send-email-imammedo@redhat.com> <34d3e078-f4e5-149e-a8ef-798d524f53a5@redhat.com> <20191206161540.1664aace@redhat.com> From: Laszlo Ersek Message-ID: Date: Fri, 6 Dec 2019 16:46:41 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20191206161540.1664aace@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-MC-Unique: 4rOCeUkbNKO63Hm1v1_Bmg-1 X-Mimecast-Spam-Score: 0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 207.211.31.120 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: pbonzini@redhat.com, philmd@redhat.com, qemu-devel@nongnu.org, mst@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 12/06/19 16:15, Igor Mammedov wrote: > On Thu, 5 Dec 2019 14:03:01 +0100 > Laszlo Ersek wrote: > >> On 12/04/19 18:05, Igor Mammedov wrote: >>> Extend CPU hotplug interface to return architecture specific >>> identifier for current CPU in 2 registers: >>> - lower 32 bits existing ACPI_CPU_CMD_DATA_OFFSET_RW >>> - upper 32 bits in new ACPI_CPU_CMD_DATA2_OFFSET_R at >>> offset 0. >> >> OK. >> >>> Target user is UEFI firmware, which needs a way to enumerate >>> all CPUs (including possible CPUs) to allocate and initialize >>> CPU structures on boot. >> >> (1) This is correct in general, but if we want to keep this description, >> then it should be moved to the commit message of the previous patch. >> CPHP_GET_CPU_ID_CMD is not needed for the purpose described above -- it >> will be necessary for handling the hotplug SMI. >> >> For the boot time allocation / initialization, the "enumerating present >> and possible CPUs" workflow is necessary, and that is documented in the >> previous patch in this series. >> >> So if we want to keep this paragraph, we should move it to the previous >> patch's commit message. >> >>> (for x86: it needs APIC ID and later command will be used to >>> retrieve ARM's MPIDR which serves the similar to APIC ID purpose) >> >> (2) I would suggest some punctuation, to make this clearer. How about: >> >>> On x86, guest UEFI firmware will use CPHP_GET_CPU_ID_CMD for fetching >>> the APIC ID when handling the hotplug SMI. >>> >>> Later, CPHP_GET_CPU_ID_CMD will be used on ARM to retrieve MPIDR, >>> which serves a purpose similar to the x86 APIC ID. > > How about following commit message: > > Firmware can enumerate present at boot APs by broadcasting wakeup IPI, > so that woken up secondary CPUs could register them-selves. > However in CPU hotplug case, it would need to know architecture > specific CPU IDs for possible and hotplugged CPUs so it could > prepare enviroment for and wake hotplugged AP. > > Reuse and extend existing CPU hotplug interface to return architecture > specific ID for currently selected CPU in 2 registers: > - lower 32 bits in ACPI_CPU_CMD_DATA_OFFSET_RW > - upper 32 bits in ACPI_CPU_CMD_DATA2_OFFSET_R > > On x86, firmware will use CPHP_GET_CPU_ID_CMD for fetching the APIC ID > when handling hotplug SMI. > > Later, CPHP_GET_CPU_ID_CMD will be used on ARM to retrieve MPIDR, > which serves the similar to APIC ID purpose. > > [...] > Looks fine to me, thank you! Laszlo