134 lines
3.9 KiB
ReStructuredText
134 lines
3.9 KiB
ReStructuredText
.. SPDX-License-Identifier: GPL-2.0
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=========
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S/390 PCI
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=========
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Authors:
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- Pierre Morel
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Copyright, IBM Corp. 2020
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Command line parameters and debugfs entries
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===========================================
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Command line parameters
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-----------------------
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* nomio
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Do not use PCI Mapped I/O (MIO) instructions.
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* norid
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Ignore the RID field and force use of one PCI domain per PCI function.
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debugfs entries
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---------------
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The S/390 debug feature (s390dbf) generates views to hold various debug results in sysfs directories of the form:
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* /sys/kernel/debug/s390dbf/pci_*/
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For example:
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- /sys/kernel/debug/s390dbf/pci_msg/sprintf
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Holds messages from the processing of PCI events, like machine check handling
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and setting of global functionality, like UID checking.
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Change the level of logging to be more or less verbose by piping
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a number between 0 and 6 to /sys/kernel/debug/s390dbf/pci_*/level. For
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details, see the documentation on the S/390 debug feature at
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Documentation/s390/s390dbf.rst.
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Sysfs entries
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=============
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Entries specific to zPCI functions and entries that hold zPCI information.
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* /sys/bus/pci/slots/XXXXXXXX
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The slot entries are set up using the function identifier (FID) of the
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PCI function. The format depicted as XXXXXXXX above is 8 hexadecimal digits
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with 0 padding and lower case hexadecimal digits.
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- /sys/bus/pci/slots/XXXXXXXX/power
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A physical function that currently supports a virtual function cannot be
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powered off until all virtual functions are removed with:
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echo 0 > /sys/bus/pci/devices/XXXX:XX:XX.X/sriov_numvf
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* /sys/bus/pci/devices/XXXX:XX:XX.X/
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- function_id
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A zPCI function identifier that uniquely identifies the function in the Z server.
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- function_handle
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Low-level identifier used for a configured PCI function.
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It might be useful for debugging.
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- pchid
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Model-dependent location of the I/O adapter.
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- pfgid
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PCI function group ID, functions that share identical functionality
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use a common identifier.
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A PCI group defines interrupts, IOMMU, IOTLB, and DMA specifics.
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- vfn
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The virtual function number, from 1 to N for virtual functions,
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0 for physical functions.
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- pft
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The PCI function type
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- port
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The port corresponds to the physical port the function is attached to.
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It also gives an indication of the physical function a virtual function
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is attached to.
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- uid
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The user identifier (UID) may be defined as part of the machine
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configuration or the z/VM or KVM guest configuration. If the accompanying
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uid_is_unique attribute is 1 the platform guarantees that the UID is unique
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within that instance and no devices with the same UID can be attached
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during the lifetime of the system.
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- uid_is_unique
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Indicates whether the user identifier (UID) is guaranteed to be and remain
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unique within this Linux instance.
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- pfip/segmentX
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The segments determine the isolation of a function.
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They correspond to the physical path to the function.
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The more the segments are different, the more the functions are isolated.
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Enumeration and hotplug
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=======================
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The PCI address consists of four parts: domain, bus, device and function,
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and is of this form: DDDD:BB:dd.f
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* When not using multi-functions (norid is set, or the firmware does not
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support multi-functions):
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- There is only one function per domain.
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- The domain is set from the zPCI function's UID as defined during the
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LPAR creation.
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* When using multi-functions (norid parameter is not set),
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zPCI functions are addressed differently:
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- There is still only one bus per domain.
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- There can be up to 256 functions per bus.
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- The domain part of the address of all functions for
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a multi-Function device is set from the zPCI function's UID as defined
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in the LPAR creation for the function zero.
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- New functions will only be ready for use after the function zero
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(the function with devfn 0) has been enumerated.
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