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Thu, 14 Jul 2022 20:12:42 +0000 (GMT) Received: from [9.171.80.107] (unknown [9.171.80.107]) by d06av26.portsmouth.uk.ibm.com (Postfix) with ESMTP; Thu, 14 Jul 2022 20:12:42 +0000 (GMT) Message-ID: Date: Thu, 14 Jul 2022 22:17:24 +0200 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.3.0 Subject: Re: [PATCH v8 08/12] s390x/cpu_topology: implementing numa for the s390x topology Content-Language: en-US To: Janis Schoetterl-Glausch , 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> <3a821cd1-b8a0-e737-5279-8ef55e58a77f@linux.ibm.com> From: Pierre Morel In-Reply-To: <3a821cd1-b8a0-e737-5279-8ef55e58a77f@linux.ibm.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: yNAmarJcmDqNgdmyQf1AIFjXjcF5wBV3 X-Proofpoint-ORIG-GUID: HhSN5O4cQlU1WYE367pZ2tDtnUWajvXt 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_17,2022-07-14_01,2022-06-22_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 clxscore=1015 impostorscore=0 priorityscore=1501 lowpriorityscore=0 malwarescore=0 mlxlogscore=999 phishscore=0 bulkscore=0 suspectscore=0 spamscore=0 mlxscore=0 adultscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2206140000 definitions=main-2207140088 Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On 7/14/22 16:57, Janis Schoetterl-Glausch wrote: > 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. > > [...] > It is a choice to have the core-id to determine were the CPU is situated in the topology. But yes we can chose the use drawer-id,book-id,socket-id and use a core-id starting on 0 on each socket. It is not done in the current implementation because the core-id implies the socket-id, book-id and drawer-id together with the smp parameters. -- Pierre Morel IBM Lab Boeblingen