8915106c69
While working on this file, also removed and unused reference in the end of the file. The reference in the text was removed by commit 9f992cca93 (spapr: update spapr hotplug documentation), but the link in the end of the document was not removed then.
Signed-off-by: Leonardo Garcia <lagarcia@br.ibm.com>
Reviewed-by: Daniel Henrique Barboza <danielhb413@gmail.com>
Message-Id: <50ed30232e0e6eafb580c17adec3fba17b873014.1641995058.git.lagarcia@br.ibm.com>
Signed-off-by: Cédric Le Goater <clg@kaod.org>
511 lines
20 KiB
Plaintext
511 lines
20 KiB
Plaintext
=============================
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sPAPR Dynamic Reconfiguration
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=============================
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sPAPR or pSeries guests make use of a facility called dynamic reconfiguration
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to handle hot plugging of dynamic "physical" resources like PCI cards, or
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"logical"/para-virtual resources like memory, CPUs, and "physical"
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host-bridges, which are generally managed by the host/hypervisor and provided
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to guests as virtualized resources. The specifics of dynamic reconfiguration
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are documented extensively in section 13 of the Linux on Power Architecture
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Reference document ([LoPAR]_). This document provides a summary of that
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information as it applies to the implementation within QEMU.
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Dynamic-reconfiguration Connectors
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==================================
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To manage hot plug/unplug of these resources, a firmware abstraction known as
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a Dynamic Resource Connector (DRC) is used to assign a particular dynamic
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resource to the guest, and provide an interface for the guest to manage
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configuration/removal of the resource associated with it.
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Device tree description of DRCs
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===============================
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A set of four Open Firmware device tree array properties are used to describe
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the name/index/power-domain/type of each DRC allocated to a guest at
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boot time. There may be multiple sets of these arrays, rooted at different
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paths in the device tree depending on the type of resource the DRCs manage.
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In some cases, the DRCs themselves may be provided by a dynamic resource,
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such as the DRCs managing PCI slots on a hot plugged PHB. In this case the
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arrays would be fetched as part of the device tree retrieval interfaces
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for hot plugged resources described under :ref:`guest-host-interface`.
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The array properties are described below. Each entry/element in an array
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describes the DRC identified by the element in the corresponding position
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of ``ibm,drc-indexes``:
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``ibm,drc-names``
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-----------------
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First 4-bytes: big-endian (BE) encoded integer denoting the number of entries.
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Each entry: a NULL-terminated ``<name>`` string encoded as a byte array.
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``<name>`` values for logical/virtual resources are defined in the Linux on
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Power Architecture Reference ([LoPAR]_) section 13.5.2.4, and basically
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consist of the type of the resource followed by a space and a numerical
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value that's unique across resources of that type.
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``<name>`` values for "physical" resources such as PCI or VIO devices are
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defined as being "location codes", which are the "location labels" of each
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encapsulating device, starting from the chassis down to the individual slot
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for the device, concatenated by a hyphen. This provides a mapping of
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resources to a physical location in a chassis for debugging purposes. For
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QEMU, this mapping is less important, so we assign a location code that
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conforms to naming specifications, but is simply a location label for the
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slot by itself to simplify the implementation. The naming convention for
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location labels is documented in detail in the [LoPAR]_ section 12.3.1.5,
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and in our case amounts to using ``C<n>`` for PCI/VIO device slots, where
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``<n>`` is unique across all PCI/VIO device slots.
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``ibm,drc-indexes``
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-------------------
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First 4-bytes: BE-encoded integer denoting the number of entries.
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Each 4-byte entry: BE-encoded ``<index>`` integer that is unique across all
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DRCs in the machine.
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``<index>`` is arbitrary, but in the case of QEMU we try to maintain the
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convention used to assign them to pSeries guests on pHyp (the hypervisor
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portion of PowerVM):
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``bit[31:28]``: integer encoding of ``<type>``, where ``<type>`` is:
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``1`` for CPU resource.
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``2`` for PHB resource.
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``3`` for VIO resource.
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``4`` for PCI resource.
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``8`` for memory resource.
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``bit[27:0]``: integer encoding of ``<id>``, where ``<id>`` is unique
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across all resources of specified type.
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``ibm,drc-power-domains``
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-------------------------
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First 4-bytes: BE-encoded integer denoting the number of entries.
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Each 4-byte entry: 32-bit, BE-encoded ``<index>`` integer that specifies the
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power domain the resource will be assigned to. In the case of QEMU we
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associated all resources with a "live insertion" domain, where the power is
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assumed to be managed automatically. The integer value for this domain is a
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special value of ``-1``.
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``ibm,drc-types``
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-----------------
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First 4-bytes: BE-encoded integer denoting the number of entries.
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Each entry: a NULL-terminated ``<type>`` string encoded as a byte array.
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``<type>`` is assigned as follows:
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"CPU" for a CPU.
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"PHB" for a physical host-bridge.
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"SLOT" for a VIO slot.
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"28" for a PCI slot.
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"MEM" for memory resource.
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.. _guest-host-interface:
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Guest->Host interface to manage dynamic resources
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=================================================
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Each DRC is given a globally unique DRC index, and resources associated with a
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particular DRC are configured/managed by the guest via a number of RTAS calls
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which reference individual DRCs based on the DRC index. This can be considered
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the guest->host interface.
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``rtas-set-power-level``
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------------------------
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Set the power level for a specified power domain.
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``arg[0]``: integer identifying power domain.
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``arg[1]``: new power level for the domain, ``0-100``.
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``output[0]``: status, ``0`` on success.
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``output[1]``: power level after command.
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``rtas-get-power-level``
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------------------------
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Get the power level for a specified power domain.
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``arg[0]``: integer identifying power domain.
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``output[0]``: status, ``0`` on success.
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``output[1]``: current power level.
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``rtas-set-indicator``
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----------------------
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Set the state of an indicator or sensor.
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``arg[0]``: integer identifying sensor/indicator type.
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``arg[1]``: index of sensor, for DR-related sensors this is generally the DRC
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index.
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``arg[2]``: desired sensor value.
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``output[0]``: status, ``0`` on success.
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For the purpose of this document we focus on the indicator/sensor types
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associated with a DRC. The types are:
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* ``9001``: ``isolation-state``, controls/indicates whether a device has been
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made accessible to a guest. Supported sensor values:
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``0``: ``isolate``, device is made inaccessible by guest OS.
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``1``: ``unisolate``, device is made available to guest OS.
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* ``9002``: ``dr-indicator``, controls "visual" indicator associated with
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device. Supported sensor values:
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``0``: ``inactive``, resource may be safely removed.
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``1``: ``active``, resource is in use and cannot be safely removed.
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``2``: ``identify``, used to visually identify slot for interactive hot plug.
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``3``: ``action``, in most cases, used in the same manner as identify.
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* ``9003``: ``allocation-state``, generally only used for "logical" DR resources
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to request the allocation/deallocation of a resource prior to acquiring it via
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``isolation-state->unisolate``, or after releasing it via
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``isolation-state->isolate``, respectively. For "physical" DR (like PCI
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hot plug/unplug) the pre-allocation of the resource is implied and this sensor
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is unused. Supported sensor values:
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``0``: ``unusable``, tell firmware/system the resource can be
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unallocated/reclaimed and added back to the system resource pool.
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``1``: ``usable``, request the resource be allocated/reserved for use by
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guest OS.
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``2``: ``exchange``, used to allocate a spare resource to use for fail-over
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in certain situations. Unused in QEMU.
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``3``: ``recover``, used to reclaim a previously allocated resource that's
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not currently allocated to the guest OS. Unused in QEMU.
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``rtas-get-sensor-state:``
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--------------------------
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Used to read an indicator or sensor value.
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``arg[0]``: integer identifying sensor/indicator type.
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``arg[1]``: index of sensor, for DR-related sensors this is generally the DRC
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index
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``output[0]``: status, 0 on success
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For DR-related operations, the only noteworthy sensor is ``dr-entity-sense``,
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which has a type value of ``9003``, as ``allocation-state`` does in the case of
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``rtas-set-indicator``. The semantics/encodings of the sensor values are
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distinct however.
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Supported sensor values for ``dr-entity-sense`` (``9003``) sensor:
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``0``: empty.
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For physical resources: DRC/slot is empty.
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For logical resources: unused.
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``1``: present.
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For physical resources: DRC/slot is populated with a device/resource.
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For logical resources: resource has been allocated to the DRC.
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``2``: unusable.
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For physical resources: unused.
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For logical resources: DRC has no resource allocated to it.
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``3``: exchange.
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For physical resources: unused.
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For logical resources: resource available for exchange (see
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``allocation-state`` sensor semantics above).
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``4``: recovery.
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For physical resources: unused.
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For logical resources: resource available for recovery (see
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``allocation-state`` sensor semantics above).
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``rtas-ibm-configure-connector``
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--------------------------------
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Used to fetch an OpenFirmware device tree description of the resource associated
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with a particular DRC.
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``arg[0]``: guest physical address of 4096-byte work area buffer.
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``arg[1]``: 0, or address of additional 4096-byte work area buffer; only
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non-zero if a prior RTAS response indicated a need for additional memory.
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``output[0]``: status:
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``0``: completed transmittal of device tree node.
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``1``: instruct guest to prepare for next device tree sibling node.
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``2``: instruct guest to prepare for next device tree child node.
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``3``: instruct guest to prepare for next device tree property.
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``4``: instruct guest to ascend to parent device tree node.
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``5``: instruct guest to provide additional work-area buffer via ``arg[1]``.
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``990x``: instruct guest that operation took too long and to try again
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later.
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The DRC index is encoded in the first 4-bytes of the first work area buffer.
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Work area (``wa``) layout, using 4-byte offsets:
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``wa[0]``: DRC index of the DRC to fetch device tree nodes from.
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``wa[1]``: ``0`` (hard-coded).
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``wa[2]``:
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For next-sibling/next-child response:
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``wa`` offset of null-terminated string denoting the new node's name.
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For next-property response:
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``wa`` offset of null-terminated string denoting new property's name.
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``wa[3]``: for next-property response (unused otherwise):
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Byte-length of new property's value.
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``wa[4]``: for next-property response (unused otherwise):
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New property's value, encoded as an OFDT-compatible byte array.
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Hot plug/unplug events
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======================
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For most DR operations, the hypervisor will issue host->guest add/remove events
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using the EPOW/check-exception notification framework, where the host issues a
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check-exception interrupt, then provides an RTAS event log via an
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rtas-check-exception call issued by the guest in response. This framework is
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documented by PAPR+ v2.7, and already use in by QEMU for generating powerdown
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requests via EPOW events.
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For DR, this framework has been extended to include hotplug events, which were
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previously unneeded due to direct manipulation of DR-related guest userspace
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tools by host-level management such as an HMC. This level of management is not
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applicable to KVM on Power, hence the reason for extending the notification
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framework to support hotplug events.
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The format for these EPOW-signalled events is described below under
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:ref:`hot-plug-unplug-event-structure`. Note that these events are not formally
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part of the PAPR+ specification, and have been superseded by a newer format,
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also described below under :ref:`hot-plug-unplug-event-structure`, and so are
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now deemed a "legacy" format. The formats are similar, but the "modern" format
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contains additional fields/flags, which are denoted for the purposes of this
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documentation with ``#ifdef GUEST_SUPPORTS_MODERN`` guards.
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QEMU should assume support only for "legacy" fields/flags unless the guest
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advertises support for the "modern" format via
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``ibm,client-architecture-support`` hcall by setting byte 5, bit 6 of it's
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``ibm,architecture-vec-5`` option vector structure (as described by [LoPAR]_,
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section B.5.2.3). As with "legacy" format events, "modern" format events are
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surfaced to the guest via check-exception RTAS calls, but use a dedicated event
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source to signal the guest. This event source is advertised to the guest by the
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addition of a ``hot-plug-events`` node under ``/event-sources`` node of the
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guest's device tree using the standard format described in [LoPAR]_,
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section B.5.12.2.
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.. _hot-plug-unplug-event-structure:
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Hot plug/unplug event structure
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===============================
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The hot plug specific payload in QEMU is implemented as follows (with all values
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encoded in big-endian format):
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.. code-block:: c
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struct rtas_event_log_v6_hp {
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#define SECTION_ID_HOTPLUG 0x4850 /* HP */
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struct section_header {
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uint16_t section_id; /* set to SECTION_ID_HOTPLUG */
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uint16_t section_length; /* sizeof(rtas_event_log_v6_hp),
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* plus the length of the DRC name
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* if a DRC name identifier is
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* specified for hotplug_identifier
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*/
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uint8_t section_version; /* version 1 */
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uint8_t section_subtype; /* unused */
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uint16_t creator_component_id; /* unused */
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} hdr;
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#define RTAS_LOG_V6_HP_TYPE_CPU 1
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#define RTAS_LOG_V6_HP_TYPE_MEMORY 2
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#define RTAS_LOG_V6_HP_TYPE_SLOT 3
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#define RTAS_LOG_V6_HP_TYPE_PHB 4
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#define RTAS_LOG_V6_HP_TYPE_PCI 5
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uint8_t hotplug_type; /* type of resource/device */
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#define RTAS_LOG_V6_HP_ACTION_ADD 1
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#define RTAS_LOG_V6_HP_ACTION_REMOVE 2
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uint8_t hotplug_action; /* action (add/remove) */
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#define RTAS_LOG_V6_HP_ID_DRC_NAME 1
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#define RTAS_LOG_V6_HP_ID_DRC_INDEX 2
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#define RTAS_LOG_V6_HP_ID_DRC_COUNT 3
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#ifdef GUEST_SUPPORTS_MODERN
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#define RTAS_LOG_V6_HP_ID_DRC_COUNT_INDEXED 4
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#endif
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uint8_t hotplug_identifier; /* type of the resource identifier,
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* which serves as the discriminator
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* for the 'drc' union field below
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*/
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#ifdef GUEST_SUPPORTS_MODERN
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uint8_t capabilities; /* capability flags, currently unused
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* by QEMU
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*/
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#else
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uint8_t reserved;
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#endif
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union {
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uint32_t index; /* DRC index of resource to take action
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* on
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*/
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uint32_t count; /* number of DR resources to take
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* action on (guest chooses which)
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*/
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#ifdef GUEST_SUPPORTS_MODERN
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struct {
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uint32_t count; /* number of DR resources to take
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* action on
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*/
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uint32_t index; /* DRC index of first resource to take
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* action on. guest will take action
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* on DRC index <index> through
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* DRC index <index + count - 1> in
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* sequential order
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*/
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} count_indexed;
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#endif
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char name[1]; /* string representing the name of the
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* DRC to take action on
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*/
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} drc;
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} QEMU_PACKED;
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``ibm,lrdr-capacity``
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=====================
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``ibm,lrdr-capacity`` is a property in the /rtas device tree node that
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identifies the dynamic reconfiguration capabilities of the guest. It consists
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of a triple consisting of ``<phys>``, ``<size>`` and ``<maxcpus>``.
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``<phys>``, encoded in BE format represents the maximum address in bytes and
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hence the maximum memory that can be allocated to the guest.
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``<size>``, encoded in BE format represents the size increments in which
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memory can be hot-plugged to the guest.
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``<maxcpus>``, a BE-encoded integer, represents the maximum number of
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processors that the guest can have.
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``pseries`` guests use this property to note the maximum allowed CPUs for the
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guest.
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``ibm,dynamic-reconfiguration-memory``
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======================================
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``ibm,dynamic-reconfiguration-memory`` is a device tree node that represents
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dynamically reconfigurable logical memory blocks (LMB). This node is generated
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only when the guest advertises the support for it via
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``ibm,client-architecture-support`` call. Memory that is not dynamically
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reconfigurable is represented by ``/memory`` nodes. The properties of this node
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that are of interest to the sPAPR memory hotplug implementation in QEMU are
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described here.
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``ibm,lmb-size``
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----------------
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This 64-bit integer defines the size of each dynamically reconfigurable LMB.
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``ibm,associativity-lookup-arrays``
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-----------------------------------
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This property defines a lookup array in which the NUMA associativity
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information for each LMB can be found. It is a property encoded array
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that begins with an integer M, the number of associativity lists followed
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by an integer N, the number of entries per associativity list and terminated
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by M associativity lists each of length N integers.
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This property provides the same information as given by ``ibm,associativity``
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property in a ``/memory`` node. Each assigned LMB has an index value between
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0 and M-1 which is used as an index into this table to select which
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associativity list to use for the LMB. This index value for each LMB is defined
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in ``ibm,dynamic-memory`` property.
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``ibm,dynamic-memory``
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----------------------
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This property describes the dynamically reconfigurable memory. It is a
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property encoded array that has an integer N, the number of LMBs followed
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by N LMB list entries.
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Each LMB list entry consists of the following elements:
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- Logical address of the start of the LMB encoded as a 64-bit integer. This
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corresponds to ``reg`` property in ``/memory`` node.
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- DRC index of the LMB that corresponds to ``ibm,my-drc-index`` property
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in a ``/memory`` node.
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- Four bytes reserved for expansion.
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- Associativity list index for the LMB that is used as an index into
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``ibm,associativity-lookup-arrays`` property described earlier. This is used
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to retrieve the right associativity list to be used for this LMB.
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- A 32-bit flags word. The bit at bit position ``0x00000008`` defines whether
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the LMB is assigned to the partition as of boot time.
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``ibm,dynamic-memory-v2``
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-------------------------
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This property describes the dynamically reconfigurable memory. This is
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an alternate and newer way to describe dynamically reconfigurable memory.
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It is a property encoded array that has an integer N (the number of
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LMB set entries) followed by N LMB set entries. There is an LMB set entry
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for each sequential group of LMBs that share common attributes.
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Each LMB set entry consists of the following elements:
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- Number of sequential LMBs in the entry represented by a 32-bit integer.
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- Logical address of the first LMB in the set encoded as a 64-bit integer.
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- DRC index of the first LMB in the set.
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- Associativity list index that is used as an index into
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``ibm,associativity-lookup-arrays`` property described earlier. This
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is used to retrieve the right associativity list to be used for all
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the LMBs in this set.
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- A 32-bit flags word that applies to all the LMBs in the set.
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