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* s390x CPU topology support
* Simplify the KVM register synchronization code * Disable the analyze-migration.py test on s390x -----BEGIN PGP SIGNATURE----- iQJFBAABCAAvFiEEJ7iIR+7gJQEY8+q5LtnXdP5wLbUFAmUyDYMRHHRodXRoQHJl ZGhhdC5jb20ACgkQLtnXdP5wLbUlgBAAkF3dvW0vMcb653sCI5vt2GHIvQQtc2Rw ghRRcTBZ7wyVxKHtqohCh7/byzDW5YEuCWUyLsc2oIz/84pc00VR/5Ng1EAxLAfe mvzzjr4jX96SmoO0DbJpqJQXaUPNYdmoshbRL0I3wkIfGtkvGRM8zHZuYINOg0hw bH6gWZ2QL/NFjXh0uAOaJB1+hRtPWvHD2rnVt0g9U9W5QhRxGJqti5YEaLBH7hh5 RydsquRZ/E6uFw4pMjjvCxDaswPwejddrP2YeR5Fd5Zo+Kzp53r9Hf/eJwlZ8yFL 5f1dRb19NZYpW1hZuJVOP8tkPydYxAM85vkUunI7Qg4gez5KI0Nz6hQozw6ufMlQ r8L17fwQMsCrwcRypImYNXyyrtHlNH5Y8FjqTct8aK64Bw3e7Qqi7d3ybFAuYZ+D k2EJ8Rlwhbg69h+Q+ucHx4NkYu9+2MFS6G7w5EcM6xl3WHSwUxh9orlEMsIkyHS3 OMFMTr1jjfFdEN6EafhPwFE/xKglFF2Fe3u6NoR+5pkv3UA5Z87giitxoekYecpH J96P3anORpWW75qvOF+nccqrd7OrUL1/yYdOyJh5Tkm0oCIeQ9E5extVf3Gne3E/ yWzr00GJRiHFO2qbGStgKHTQLItgQpccwNpSzEdgHCqwLbXl6e3Hoq42VIFOlbN/ ZtgpyUkuYyQ= =xDb+ -----END PGP SIGNATURE----- Merge tag 'pull-request-2023-10-20' of https://gitlab.com/thuth/qemu into staging * s390x CPU topology support * Simplify the KVM register synchronization code * Disable the analyze-migration.py test on s390x # -----BEGIN PGP SIGNATURE----- # # iQJFBAABCAAvFiEEJ7iIR+7gJQEY8+q5LtnXdP5wLbUFAmUyDYMRHHRodXRoQHJl # ZGhhdC5jb20ACgkQLtnXdP5wLbUlgBAAkF3dvW0vMcb653sCI5vt2GHIvQQtc2Rw # ghRRcTBZ7wyVxKHtqohCh7/byzDW5YEuCWUyLsc2oIz/84pc00VR/5Ng1EAxLAfe # mvzzjr4jX96SmoO0DbJpqJQXaUPNYdmoshbRL0I3wkIfGtkvGRM8zHZuYINOg0hw # bH6gWZ2QL/NFjXh0uAOaJB1+hRtPWvHD2rnVt0g9U9W5QhRxGJqti5YEaLBH7hh5 # RydsquRZ/E6uFw4pMjjvCxDaswPwejddrP2YeR5Fd5Zo+Kzp53r9Hf/eJwlZ8yFL # 5f1dRb19NZYpW1hZuJVOP8tkPydYxAM85vkUunI7Qg4gez5KI0Nz6hQozw6ufMlQ # r8L17fwQMsCrwcRypImYNXyyrtHlNH5Y8FjqTct8aK64Bw3e7Qqi7d3ybFAuYZ+D # k2EJ8Rlwhbg69h+Q+ucHx4NkYu9+2MFS6G7w5EcM6xl3WHSwUxh9orlEMsIkyHS3 # OMFMTr1jjfFdEN6EafhPwFE/xKglFF2Fe3u6NoR+5pkv3UA5Z87giitxoekYecpH # J96P3anORpWW75qvOF+nccqrd7OrUL1/yYdOyJh5Tkm0oCIeQ9E5extVf3Gne3E/ # yWzr00GJRiHFO2qbGStgKHTQLItgQpccwNpSzEdgHCqwLbXl6e3Hoq42VIFOlbN/ # ZtgpyUkuYyQ= # =xDb+ # -----END PGP SIGNATURE----- # gpg: Signature made Thu 19 Oct 2023 22:17:55 PDT # gpg: using RSA key 27B88847EEE0250118F3EAB92ED9D774FE702DB5 # gpg: issuer "thuth@redhat.com" # gpg: Good signature from "Thomas Huth <th.huth@gmx.de>" [full] # gpg: aka "Thomas Huth <thuth@redhat.com>" [full] # gpg: aka "Thomas Huth <huth@tuxfamily.org>" [full] # gpg: aka "Thomas Huth <th.huth@posteo.de>" [unknown] # Primary key fingerprint: 27B8 8847 EEE0 2501 18F3 EAB9 2ED9 D774 FE70 2DB5 * tag 'pull-request-2023-10-20' of https://gitlab.com/thuth/qemu: (24 commits) tests/qtest/migration-test: Disable the analyze-migration.py test on s390x target/s390x/kvm: Simplify the GPRs, ACRs, CRs and prefix synchronization code target/s390x/kvm: Turn KVM_CAP_SYNC_REGS into a hard requirement tests/avocado: s390x cpu topology bad move tests/avocado: s390x cpu topology dedicated errors tests/avocado: s390x cpu topology test socket full tests/avocado: s390x cpu topology test dedicated CPU tests/avocado: s390x cpu topology entitlement tests tests/avocado: s390x cpu topology polarization tests/avocado: s390x cpu topology core docs/s390x/cpu topology: document s390x cpu topology qapi/s390x/cpu topology: add query-s390x-cpu-polarization command qapi/s390x/cpu topology: CPU_POLARIZATION_CHANGE QAPI event machine: adding s390 topology to info hotpluggable-cpus machine: adding s390 topology to query-cpu-fast qapi/s390x/cpu topology: set-cpu-topology qmp command target/s390x/cpu topology: activate CPU topology s390x/cpu topology: interception of PTF instruction s390x/cpu topology: resetting the Topology-Change-Report s390x/sclp: reporting the maximum nested topology entries ... Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This commit is contained in:
Stefan Hajnoczi
commit
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35 changed files with 2288 additions and 128 deletions
244
docs/system/s390x/cpu-topology.rst
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docs/system/s390x/cpu-topology.rst
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.. _cpu-topology-s390x:
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CPU topology on s390x
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=====================
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Since QEMU 8.2, CPU topology on s390x provides up to 3 levels of
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topology containers: drawers, books and sockets. They define a
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tree-shaped hierarchy.
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The socket container has one or more CPU entries.
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Each of these CPU entries consists of a bitmap and three CPU attributes:
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- CPU type
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- entitlement
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- dedication
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Each bit set in the bitmap correspond to a core-id of a vCPU with matching
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attributes.
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This documentation provides general information on S390 CPU topology,
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how to enable it and explains the new CPU attributes.
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For information on how to modify the S390 CPU topology and how to
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monitor polarization changes, see ``docs/devel/s390-cpu-topology.rst``.
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Prerequisites
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-------------
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To use the CPU topology, you need to run with KVM on a s390x host that
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uses the Linux kernel v6.0 or newer (which provide the so-called
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``KVM_CAP_S390_CPU_TOPOLOGY`` capability that allows QEMU to signal the
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CPU topology facility via the so-called STFLE bit 11 to the VM).
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Enabling CPU topology
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---------------------
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Currently, CPU topology is only enabled in the host model by default.
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Enabling CPU topology in a CPU model is done by setting the CPU flag
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``ctop`` to ``on`` as in:
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.. code-block:: bash
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-cpu gen16b,ctop=on
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Having the topology disabled by default allows migration between
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old and new QEMU without adding new flags.
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Default topology usage
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----------------------
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The CPU topology can be specified on the QEMU command line
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with the ``-smp`` or the ``-device`` QEMU command arguments.
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Note also that since 7.2 threads are no longer supported in the topology
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and the ``-smp`` command line argument accepts only ``threads=1``.
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If none of the containers attributes (drawers, books, sockets) are
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specified for the ``-smp`` flag, the number of these containers
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is 1.
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Thus the following two options will result in the same topology:
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.. code-block:: bash
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-smp cpus=5,drawer=1,books=1,sockets=8,cores=4,maxcpus=32
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and
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.. code-block:: bash
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-smp cpus=5,sockets=8,cores=4,maxcpus=32
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When a CPU is defined by the ``-smp`` command argument, its position
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inside the topology is calculated by adding the CPUs to the topology
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based on the core-id starting with core-0 at position 0 of socket-0,
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book-0, drawer-0 and filling all CPUs of socket-0 before filling socket-1
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of book-0 and so on up to the last socket of the last book of the last
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drawer.
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When a CPU is defined by the ``-device`` command argument, the
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tree topology attributes must all be defined or all not defined.
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.. code-block:: bash
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-device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=1
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or
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.. code-block:: bash
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-device gen16b-s390x-cpu,core-id=1,dedicated=true
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If none of the tree attributes (drawer, book, sockets), are specified
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for the ``-device`` argument, like for all CPUs defined with the ``-smp``
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command argument the topology tree attributes will be set by simply
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adding the CPUs to the topology based on the core-id.
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QEMU will not try to resolve collisions and will report an error if the
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CPU topology defined explicitly or implicitly on a ``-device``
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argument collides with the definition of a CPU implicitly defined
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on the ``-smp`` argument.
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When the topology modifier attributes are not defined for the
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``-device`` command argument they takes following default values:
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- dedicated: ``false``
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- entitlement: ``medium``
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Hot plug
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++++++++
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New CPUs can be plugged using the device_add hmp command as in:
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.. code-block:: bash
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(qemu) device_add gen16b-s390x-cpu,core-id=9
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The placement of the CPU is derived from the core-id as described above.
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The topology can of course also be fully defined:
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.. code-block:: bash
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(qemu) device_add gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=1
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Examples
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++++++++
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In the following machine we define 8 sockets with 4 cores each.
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.. code-block:: bash
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$ qemu-system-s390x -m 2G \
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-cpu gen16b,ctop=on \
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-smp cpus=5,sockets=8,cores=4,maxcpus=32 \
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-device host-s390x-cpu,core-id=14 \
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A new CPUs can be plugged using the device_add hmp command as before:
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.. code-block:: bash
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(qemu) device_add gen16b-s390x-cpu,core-id=9
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The core-id defines the placement of the core in the topology by
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starting with core 0 in socket 0 up to maxcpus.
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In the example above:
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* There are 5 CPUs provided to the guest with the ``-smp`` command line
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They will take the core-ids 0,1,2,3,4
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As we have 4 cores in a socket, we have 4 CPUs provided
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to the guest in socket 0, with core-ids 0,1,2,3.
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The last CPU, with core-id 4, will be on socket 1.
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* the core with ID 14 provided by the ``-device`` command line will
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be placed in socket 3, with core-id 14
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* the core with ID 9 provided by the ``device_add`` qmp command will
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be placed in socket 2, with core-id 9
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Polarization, entitlement and dedication
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----------------------------------------
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Polarization
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++++++++++++
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The polarization affects how the CPUs of a shared host are utilized/distributed
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among guests.
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The guest determines the polarization by using the PTF instruction.
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Polarization defines two models of CPU provisioning: horizontal
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and vertical.
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The horizontal polarization is the default model on boot and after
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subsystem reset. When horizontal polarization is in effect all vCPUs should
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have about equal resource provisioning.
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In the vertical polarization model vCPUs are unequal, but overall more resources
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might be available.
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The guest can make use of the vCPU entitlement information provided by the host
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to optimize kernel thread scheduling.
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A subsystem reset puts all vCPU of the configuration into the
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horizontal polarization.
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Entitlement
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+++++++++++
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The vertical polarization specifies that the guest's vCPU can get
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different real CPU provisioning:
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- a vCPU with vertical high entitlement specifies that this
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vCPU gets 100% of the real CPU provisioning.
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- a vCPU with vertical medium entitlement specifies that this
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vCPU shares the real CPU with other vCPUs.
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- a vCPU with vertical low entitlement specifies that this
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vCPU only gets real CPU provisioning when no other vCPUs needs it.
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In the case a vCPU with vertical high entitlement does not use
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the real CPU, the unused "slack" can be dispatched to other vCPU
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with medium or low entitlement.
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A vCPU can be "dedicated" in which case the vCPU is fully dedicated to a single
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real CPU.
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The dedicated bit is an indication of affinity of a vCPU for a real CPU
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while the entitlement indicates the sharing or exclusivity of use.
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Defining the topology on the command line
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-----------------------------------------
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The topology can entirely be defined using -device cpu statements,
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with the exception of CPU 0 which must be defined with the -smp
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argument.
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For example, here we set the position of the cores 1,2,3 to
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drawer 1, book 1, socket 2 and cores 0,9 and 14 to drawer 0,
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book 0, socket 0 without defining entitlement or dedication.
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Core 4 will be set on its default position on socket 1
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(since we have 4 core per socket) and we define it as dedicated and
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with vertical high entitlement.
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.. code-block:: bash
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$ qemu-system-s390x -m 2G \
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-cpu gen16b,ctop=on \
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-smp cpus=1,sockets=8,cores=4,maxcpus=32 \
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\
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-device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=1 \
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-device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=2 \
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-device gen16b-s390x-cpu,drawer-id=1,book-id=1,socket-id=2,core-id=3 \
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\
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-device gen16b-s390x-cpu,drawer-id=0,book-id=0,socket-id=0,core-id=9 \
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-device gen16b-s390x-cpu,drawer-id=0,book-id=0,socket-id=0,core-id=14 \
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\
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-device gen16b-s390x-cpu,core-id=4,dedicated=on,entitlement=high
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The entitlement defined for the CPU 4 will only be used after the guest
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successfully enables vertical polarization by using the PTF instruction.
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@ -34,3 +34,4 @@ Architectural features
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.. toctree::
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s390x/bootdevices
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s390x/protvirt
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s390x/cpu-topology
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