{"id":1850824,"url":"http://patchwork.ozlabs.org/api/patches/1850824/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20231018130716.286638-15-thuth@redhat.com/","project":{"id":14,"url":"http://patchwork.ozlabs.org/api/projects/14/?format=json","name":"QEMU Development","link_name":"qemu-devel","list_id":"qemu-devel.nongnu.org","list_email":"qemu-devel@nongnu.org","web_url":"","scm_url":"","webscm_url":"","list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20231018130716.286638-15-thuth@redhat.com>","list_archive_url":null,"date":"2023-10-18T13:07:05","name":"[PULL,14/25] docs/s390x/cpu topology: document s390x cpu topology","commit_ref":null,"pull_url":null,"state":"new","archived":false,"hash":"6f63021302db4ba89476382369962ab9f3e9b91e","submitter":{"id":66152,"url":"http://patchwork.ozlabs.org/api/people/66152/?format=json","name":"Thomas Huth","email":"thuth@redhat.com"},"delegate":null,"mbox":"http://patchwork.ozlabs.org/project/qemu-devel/patch/20231018130716.286638-15-thuth@redhat.com/mbox/","series":[{"id":378180,"url":"http://patchwork.ozlabs.org/api/series/378180/?format=json","web_url":"http://patchwork.ozlabs.org/project/qemu-devel/list/?series=378180","date":"2023-10-18T13:06:52","name":"[PULL,01/25] qapi: machine.json: change docs regarding CPU topology","version":1,"mbox":"http://patchwork.ozlabs.org/series/378180/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/1850824/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/1850824/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"incoming@patchwork.ozlabs.org","Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (1024-bit key;\n unprotected) header.d=redhat.com header.i=@redhat.com header.a=rsa-sha256\n header.s=mimecast20190719 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","Errors-To":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org","Sender":"qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org"},"content":"From: Pierre Morel \n\nAdd some basic examples for the definition of cpu topology\nin s390x.\n\nSigned-off-by: Pierre Morel \nCo-developed-by: Nina Schoetterl-Glausch \nReviewed-by: Thomas Huth \nSigned-off-by: Nina Schoetterl-Glausch \nMessage-ID: <20231016183925.2384704-15-nsg@linux.ibm.com>\nSigned-off-by: Thomas Huth \n---\n MAINTAINERS | 2 +\n docs/devel/index-internals.rst | 1 +\n docs/devel/s390-cpu-topology.rst | 170 ++++++++++++++++++++\n docs/system/s390x/cpu-topology.rst | 244 +++++++++++++++++++++++++++++\n docs/system/target-s390x.rst | 1 +\n qapi/machine.json | 2 +\n 6 files changed, 420 insertions(+)\n create mode 100644 docs/devel/s390-cpu-topology.rst\n create mode 100644 docs/system/s390x/cpu-topology.rst","diff":"diff --git a/MAINTAINERS b/MAINTAINERS\nindex cfc37e9af7..de8d9f5104 100644\n--- a/MAINTAINERS\n+++ b/MAINTAINERS\n@@ -1716,6 +1716,8 @@ S: Supported\n F: include/hw/s390x/cpu-topology.h\n F: hw/s390x/cpu-topology.c\n F: target/s390x/kvm/stsi-topology.c\n+F: docs/devel/s390-cpu-topology.rst\n+F: docs/system/s390x/cpu-topology.rst\n \n X86 Machines\n ------------\ndiff --git a/docs/devel/index-internals.rst b/docs/devel/index-internals.rst\nindex e1a93df263..6f81df92bc 100644\n--- a/docs/devel/index-internals.rst\n+++ b/docs/devel/index-internals.rst\n@@ -14,6 +14,7 @@ Details about QEMU's various subsystems including how to add features to them.\n migration\n multi-process\n reset\n+ s390-cpu-topology\n s390-dasd-ipl\n tracing\n vfio-migration\ndiff --git a/docs/devel/s390-cpu-topology.rst b/docs/devel/s390-cpu-topology.rst\nnew file mode 100644\nindex 0000000000..9eab28d5e5\n--- /dev/null\n+++ b/docs/devel/s390-cpu-topology.rst\n@@ -0,0 +1,170 @@\n+QAPI interface for S390 CPU topology\n+====================================\n+\n+The following sections will explain the QAPI interface for S390 CPU topology\n+with the help of exemplary output.\n+For this, let's assume that QEMU has been started with the following\n+command, defining 4 CPUs, where CPU[0] is defined by the -smp argument and will\n+have default values:\n+\n+.. code-block:: bash\n+\n+ qemu-system-s390x \\\n+ -enable-kvm \\\n+ -cpu z14,ctop=on \\\n+ -smp 1,drawers=3,books=3,sockets=2,cores=2,maxcpus=36 \\\n+ -device z14-s390x-cpu,core-id=19,entitlement=high \\\n+ -device z14-s390x-cpu,core-id=11,entitlement=low \\\n+ -device z14-s390x-cpu,core-id=112,entitlement=high \\\n+ ...\n+\n+Additions to query-cpus-fast\n+----------------------------\n+\n+The command query-cpus-fast allows querying the topology tree and\n+modifiers for all configured vCPUs.\n+\n+.. code-block:: QMP\n+\n+ { \"execute\": \"query-cpus-fast\" }\n+ {\n+ \"return\": [\n+ {\n+ \"dedicated\": false,\n+ \"thread-id\": 536993,\n+ \"props\": {\n+ \"core-id\": 0,\n+ \"socket-id\": 0,\n+ \"drawer-id\": 0,\n+ \"book-id\": 0\n+ },\n+ \"cpu-state\": \"operating\",\n+ \"entitlement\": \"medium\",\n+ \"qom-path\": \"/machine/unattached/device[0]\",\n+ \"cpu-index\": 0,\n+ \"target\": \"s390x\"\n+ },\n+ {\n+ \"dedicated\": false,\n+ \"thread-id\": 537003,\n+ \"props\": {\n+ \"core-id\": 19,\n+ \"socket-id\": 1,\n+ \"drawer-id\": 0,\n+ \"book-id\": 2\n+ },\n+ \"cpu-state\": \"operating\",\n+ \"entitlement\": \"high\",\n+ \"qom-path\": \"/machine/peripheral-anon/device[0]\",\n+ \"cpu-index\": 19,\n+ \"target\": \"s390x\"\n+ },\n+ {\n+ \"dedicated\": false,\n+ \"thread-id\": 537004,\n+ \"props\": {\n+ \"core-id\": 11,\n+ \"socket-id\": 1,\n+ \"drawer-id\": 0,\n+ \"book-id\": 1\n+ },\n+ \"cpu-state\": \"operating\",\n+ \"entitlement\": \"low\",\n+ \"qom-path\": \"/machine/peripheral-anon/device[1]\",\n+ \"cpu-index\": 11,\n+ \"target\": \"s390x\"\n+ },\n+ {\n+ \"dedicated\": true,\n+ \"thread-id\": 537005,\n+ \"props\": {\n+ \"core-id\": 112,\n+ \"socket-id\": 0,\n+ \"drawer-id\": 3,\n+ \"book-id\": 2\n+ },\n+ \"cpu-state\": \"operating\",\n+ \"entitlement\": \"high\",\n+ \"qom-path\": \"/machine/peripheral-anon/device[2]\",\n+ \"cpu-index\": 112,\n+ \"target\": \"s390x\"\n+ }\n+ ]\n+ }\n+\n+\n+QAPI command: set-cpu-topology\n+------------------------------\n+\n+The command set-cpu-topology allows modifying the topology tree\n+or the topology modifiers of a vCPU in the configuration.\n+\n+.. code-block:: QMP\n+\n+ { \"execute\": \"set-cpu-topology\",\n+ \"arguments\": {\n+ \"core-id\": 11,\n+ \"socket-id\": 0,\n+ \"book-id\": 0,\n+ \"drawer-id\": 0,\n+ \"entitlement\": \"low\",\n+ \"dedicated\": false\n+ }\n+ }\n+ {\"return\": {}}\n+\n+The core-id parameter is the only mandatory parameter and every\n+unspecified parameter keeps its previous value.\n+\n+QAPI event CPU_POLARIZATION_CHANGE\n+----------------------------------\n+\n+When a guest requests a modification of the polarization,\n+QEMU sends a CPU_POLARIZATION_CHANGE event.\n+\n+When requesting the change, the guest only specifies horizontal or\n+vertical polarization.\n+It is the job of the entity administrating QEMU to set the dedication and fine\n+grained vertical entitlement in response to this event.\n+\n+Note that a vertical polarized dedicated vCPU can only have a high\n+entitlement, giving 6 possibilities for vCPU polarization:\n+\n+- Horizontal\n+- Horizontal dedicated\n+- Vertical low\n+- Vertical medium\n+- Vertical high\n+- Vertical high dedicated\n+\n+Example of the event received when the guest issues the CPU instruction\n+Perform Topology Function PTF(0) to request an horizontal polarization:\n+\n+.. code-block:: QMP\n+\n+ {\n+ \"timestamp\": {\n+ \"seconds\": 1687870305,\n+ \"microseconds\": 566299\n+ },\n+ \"event\": \"CPU_POLARIZATION_CHANGE\",\n+ \"data\": {\n+ \"polarization\": \"horizontal\"\n+ }\n+ }\n+\n+QAPI query command: query-s390x-cpu-polarization\n+------------------------------------------------\n+\n+The query command query-s390x-cpu-polarization returns the current\n+CPU polarization of the machine.\n+In this case the guest previously issued a PTF(1) to request vertical polarization:\n+\n+.. code-block:: QMP\n+\n+ { \"execute\": \"query-s390x-cpu-polarization\" }\n+ {\n+ \"return\": {\n+ \"polarization\": \"vertical\"\n+ }\n+ }\ndiff --git a/docs/system/s390x/cpu-topology.rst b/docs/system/s390x/cpu-topology.rst\nnew file mode 100644\nindex 0000000000..5133fdc362\n--- /dev/null\n+++ b/docs/system/s390x/cpu-topology.rst\n@@ -0,0 +1,244 @@\n+.. _cpu-topology-s390x:\n+\n+CPU topology on s390x\n+=====================\n+\n+Since QEMU 8.2, CPU topology on s390x provides up to 3 levels of\n+topology containers: drawers, books and sockets. They define a\n+tree-shaped hierarchy.\n+\n+The socket container has one or more CPU entries.\n+Each of these CPU entries consists of a bitmap and three CPU attributes:\n+\n+- CPU type\n+- entitlement\n+- dedication\n+\n+Each bit set in the bitmap correspond to a core-id of a vCPU with matching\n+attributes.\n+\n+This documentation provides general information on S390 CPU topology,\n+how to enable it and explains the new CPU attributes.\n+For information on how to modify the S390 CPU topology and how to\n+monitor polarization changes, see ``docs/devel/s390-cpu-topology.rst``.\n+\n+Prerequisites\n+-------------\n+\n+To use the CPU topology, you need to run with KVM on a s390x host that\n+uses the Linux kernel v6.0 or newer (which provide the so-called\n+``KVM_CAP_S390_CPU_TOPOLOGY`` capability that allows QEMU to signal the\n+CPU topology facility via the so-called STFLE bit 11 to the VM).\n+\n+Enabling CPU topology\n+---------------------\n+\n+Currently, CPU topology is only enabled in the host model by default.\n+\n+Enabling CPU topology in a CPU model is done by setting the CPU flag\n+``ctop`` to ``on`` as in:\n+\n+.. code-block:: bash\n+\n+ -cpu gen16b,ctop=on\n+\n+Having the topology disabled by default allows migration between\n+old and new QEMU without adding new flags.\n+\n+Default topology usage\n+----------------------\n+\n+The CPU topology can be specified on the QEMU command line\n+with the ``-smp`` or the ``-device`` QEMU command arguments.\n+\n+Note also that since 7.2 threads are no longer supported in the topology\n+and the ``-smp`` command line argument accepts only ``threads=1``.\n+\n+If none of the containers attributes (drawers, books, sockets) are\n+specified for the ``-smp`` flag, the number of these containers\n+is 1.\n+\n+Thus the following two options will result in the same topology:\n+\n+.. code-block:: bash\n+\n+ -smp cpus=5,drawer=1,books=1,sockets=8,cores=4,maxcpus=32\n+\n+and\n+\n+.. code-block:: bash\n+\n+ -smp cpus=5,sockets=8,cores=4,maxcpus=32\n+\n+When a CPU is defined by the ``-smp`` command argument, its position\n+inside the topology is calculated by adding the CPUs to the topology\n+based on the core-id starting with core-0 at position 0 of socket-0,\n+book-0, drawer-0 and filling all CPUs of socket-0 before filling socket-1\n+of book-0 and so on up to the last socket of the last book of the last\n+drawer.\n+\n+When a CPU is defined by the ``-device`` command argument, the\n+tree topology attributes must all be defined or all not defined.\n+\n+.. code-block:: bash\n+\n+ -device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=1\n+\n+or\n+\n+.. code-block:: bash\n+\n+ -device gen16b-s390x-cpu,core-id=1,dedicated=true\n+\n+If none of the tree attributes (drawer, book, sockets), are specified\n+for the ``-device`` argument, like for all CPUs defined with the ``-smp``\n+command argument the topology tree attributes will be set by simply\n+adding the CPUs to the topology based on the core-id.\n+\n+QEMU will not try to resolve collisions and will report an error if the\n+CPU topology defined explicitly or implicitly on a ``-device``\n+argument collides with the definition of a CPU implicitly defined\n+on the ``-smp`` argument.\n+\n+When the topology modifier attributes are not defined for the\n+``-device`` command argument they takes following default values:\n+\n+- dedicated: ``false``\n+- entitlement: ``medium``\n+\n+\n+Hot plug\n+++++++++\n+\n+New CPUs can be plugged using the device_add hmp command as in:\n+\n+.. code-block:: bash\n+\n+ (qemu) device_add gen16b-s390x-cpu,core-id=9\n+\n+The placement of the CPU is derived from the core-id as described above.\n+\n+The topology can of course also be fully defined:\n+\n+.. code-block:: bash\n+\n+ (qemu) device_add gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=1\n+\n+\n+Examples\n+++++++++\n+\n+In the following machine we define 8 sockets with 4 cores each.\n+\n+.. code-block:: bash\n+\n+ $ qemu-system-s390x -m 2G \\\n+ -cpu gen16b,ctop=on \\\n+ -smp cpus=5,sockets=8,cores=4,maxcpus=32 \\\n+ -device host-s390x-cpu,core-id=14 \\\n+\n+A new CPUs can be plugged using the device_add hmp command as before:\n+\n+.. code-block:: bash\n+\n+ (qemu) device_add gen16b-s390x-cpu,core-id=9\n+\n+The core-id defines the placement of the core in the topology by\n+starting with core 0 in socket 0 up to maxcpus.\n+\n+In the example above:\n+\n+* There are 5 CPUs provided to the guest with the ``-smp`` command line\n+ They will take the core-ids 0,1,2,3,4\n+ As we have 4 cores in a socket, we have 4 CPUs provided\n+ to the guest in socket 0, with core-ids 0,1,2,3.\n+ The last CPU, with core-id 4, will be on socket 1.\n+\n+* the core with ID 14 provided by the ``-device`` command line will\n+ be placed in socket 3, with core-id 14\n+\n+* the core with ID 9 provided by the ``device_add`` qmp command will\n+ be placed in socket 2, with core-id 9\n+\n+\n+Polarization, entitlement and dedication\n+----------------------------------------\n+\n+Polarization\n+++++++++++++\n+\n+The polarization affects how the CPUs of a shared host are utilized/distributed\n+among guests.\n+The guest determines the polarization by using the PTF instruction.\n+\n+Polarization defines two models of CPU provisioning: horizontal\n+and vertical.\n+\n+The horizontal polarization is the default model on boot and after\n+subsystem reset. When horizontal polarization is in effect all vCPUs should\n+have about equal resource provisioning.\n+\n+In the vertical polarization model vCPUs are unequal, but overall more resources\n+might be available.\n+The guest can make use of the vCPU entitlement information provided by the host\n+to optimize kernel thread scheduling.\n+\n+A subsystem reset puts all vCPU of the configuration into the\n+horizontal polarization.\n+\n+Entitlement\n++++++++++++\n+\n+The vertical polarization specifies that the guest's vCPU can get\n+different real CPU provisioning:\n+\n+- a vCPU with vertical high entitlement specifies that this\n+ vCPU gets 100% of the real CPU provisioning.\n+\n+- a vCPU with vertical medium entitlement specifies that this\n+ vCPU shares the real CPU with other vCPUs.\n+\n+- a vCPU with vertical low entitlement specifies that this\n+ vCPU only gets real CPU provisioning when no other vCPUs needs it.\n+\n+In the case a vCPU with vertical high entitlement does not use\n+the real CPU, the unused \"slack\" can be dispatched to other vCPU\n+with medium or low entitlement.\n+\n+A vCPU can be \"dedicated\" in which case the vCPU is fully dedicated to a single\n+real CPU.\n+\n+The dedicated bit is an indication of affinity of a vCPU for a real CPU\n+while the entitlement indicates the sharing or exclusivity of use.\n+\n+Defining the topology on the command line\n+-----------------------------------------\n+\n+The topology can entirely be defined using -device cpu statements,\n+with the exception of CPU 0 which must be defined with the -smp\n+argument.\n+\n+For example, here we set the position of the cores 1,2,3 to\n+drawer 1, book 1, socket 2 and cores 0,9 and 14 to drawer 0,\n+book 0, socket 0 without defining entitlement or dedication.\n+Core 4 will be set on its default position on socket 1\n+(since we have 4 core per socket) and we define it as dedicated and\n+with vertical high entitlement.\n+\n+.. code-block:: bash\n+\n+ $ qemu-system-s390x -m 2G \\\n+ -cpu gen16b,ctop=on \\\n+ -smp cpus=1,sockets=8,cores=4,maxcpus=32 \\\n+ \\\n+ -device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=1 \\\n+ -device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=2 \\\n+ -device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=3 \\\n+ \\\n+ -device gen16b-s390x-cpu,drawer-id=0,book-id=0,socket-id=0,core-id=9 \\\n+ -device gen16b-s390x-cpu,drawer-id=0,book-id=0,socket-id=0,core-id=14 \\\n+ \\\n+ -device gen16b-s390x-cpu,core-id=4,dedicated=on,entitlement=high\n+\n+The entitlement defined for the CPU 4 will only be used after the guest\n+successfully enables vertical polarization by using the PTF instruction.\ndiff --git a/docs/system/target-s390x.rst b/docs/system/target-s390x.rst\nindex f6f11433c7..94c981e732 100644\n--- a/docs/system/target-s390x.rst\n+++ b/docs/system/target-s390x.rst\n@@ -34,3 +34,4 @@ Architectural features\n .. toctree::\n s390x/bootdevices\n s390x/protvirt\n+ s390x/cpu-topology\ndiff --git a/qapi/machine.json b/qapi/machine.json\nindex b4bd26f716..6c9d2f6dcf 100644\n--- a/qapi/machine.json\n+++ b/qapi/machine.json\n@@ -909,6 +909,8 @@\n # Which members are optional and which mandatory depends on the\n # architecture and board.\n #\n+# For s390x see :ref:`cpu-topology-s390x`.\n+#\n # The ids other than the node-id specify the position of the CPU\n # within the CPU topology (as defined by the machine property \"smp\",\n # thus see also type @SMPConfiguration)\n","prefixes":["PULL","14/25"]}