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Thu, 14 Jul 2022 14:57:55 +0000 (GMT) Received: from d06av23.portsmouth.uk.ibm.com (unknown [127.0.0.1]) by IMSVA (Postfix) with ESMTP id AD097A4051; Thu, 14 Jul 2022 14:57:46 +0000 (GMT) Received: from [9.171.84.216] (unknown [9.171.84.216]) by d06av23.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 14 Jul 2022 14:57:46 +0000 (GMT) Message-ID: <3a821cd1-b8a0-e737-5279-8ef55e58a77f@linux.ibm.com> Date: Thu, 14 Jul 2022 16:57:46 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v8 08/12] s390x/cpu_topology: implementing numa for the s390x topology Content-Language: en-US To: Pierre Morel , qemu-s390x@nongnu.org Cc: qemu-devel@nongnu.org, borntraeger@de.ibm.com, pasic@linux.ibm.com, richard.henderson@linaro.org, david@redhat.com, thuth@redhat.com, cohuck@redhat.com, mst@redhat.com, pbonzini@redhat.com, kvm@vger.kernel.org, ehabkost@redhat.com, marcel.apfelbaum@gmail.com, eblake@redhat.com, armbru@redhat.com, seiden@linux.ibm.com, nrb@linux.ibm.com, frankja@linux.ibm.com References: <20220620140352.39398-1-pmorel@linux.ibm.com> <20220620140352.39398-9-pmorel@linux.ibm.com> From: Janis Schoetterl-Glausch In-Reply-To: <20220620140352.39398-9-pmorel@linux.ibm.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: ep_XZITM-z0Mg8GeoK2FTcAVaFBG4uDq X-Proofpoint-ORIG-GUID: D6hF0RvvpIEj6j5ZvKUMfMK-tH1tU32k X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.205,Aquarius:18.0.883,Hydra:6.0.517,FMLib:17.11.122.1 definitions=2022-07-14_10,2022-07-14_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 spamscore=0 clxscore=1015 mlxscore=0 suspectscore=0 bulkscore=0 mlxlogscore=999 phishscore=0 priorityscore=1501 impostorscore=0 malwarescore=0 lowpriorityscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207140062 Received-SPF: pass client-ip=148.163.156.1; envelope-from=scgl@linux.ibm.com; helo=mx0a-001b2d01.pphosted.com X-Spam_score_int: -19 X-Spam_score: -2.0 X-Spam_bar: -- X-Spam_report: (-2.0 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.001, RCVD_IN_MSPIKE_H2=-0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 6/20/22 16:03, Pierre Morel wrote: > S390x CPU Topology allows a non uniform repartition of the CPU > inside the topology containers, sockets, books and drawers. > > We use numa to place the CPU inside the right topology container > and report the non uniform topology to the guest. > > Note that s390x needs CPU0 to belong to the topology and consequently > all topology must include CPU0. > > We accept a partial QEMU numa definition, in that case undefined CPUs > are added to free slots in the topology starting with slot 0 and going > up. I don't understand why doing it this way, via numa, makes sense for us. We report the topology to the guest via STSI, which tells the guest what the topology "tree" looks like. We don't report any numa distances to the guest. The natural way to specify where a cpu is added to the vm, seems to me to be by specify the socket, book, ... IDs when doing a device_add or via -device on the command line. [...]