Documentation/arch/s390/pci.rst

Source file repositories/reference/linux-study-clean/Documentation/arch/s390/pci.rst

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Documentation/arch/s390/pci.rst
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Repository support layer: documentation, build tooling, samples, user-space helper tools, generated initramfs support, licenses, and validation utilities.

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.. SPDX-License-Identifier: GPL-2.0

=========
S/390 PCI
=========

Authors:
        - Pierre Morel
        - Niklas Schnelle

Copyright, IBM Corp. 2020


Command line parameters and debugfs entries
===========================================

Command line parameters
-----------------------

* nomio

  Do not use PCI Mapped I/O (MIO) instructions.

* norid

  Ignore the RID field and force use of one PCI domain per PCI function.

debugfs entries
---------------

The S/390 debug feature (s390dbf) generates views to hold various debug results
in sysfs directories of the form:

 * /sys/kernel/debug/s390dbf/pci_*/

For example:

  - /sys/kernel/debug/s390dbf/pci_msg/sprintf

    holds messages from the processing of PCI events, like machine check handling
    and setting of global functionality, like UID checking.

  Change the level of logging to be more or less verbose by piping
  a number between 0 and 6 to  /sys/kernel/debug/s390dbf/pci_*/level. For
  details, see the documentation on the S/390 debug feature at
  Documentation/arch/s390/s390dbf.rst.

Sysfs entries
=============

Entries specific to zPCI functions and entries that hold zPCI information.

* /sys/bus/pci/slots/XXXXXXXX:

  The slot entries are set up using the function identifier (FID) of the PCI
  function as slot name. The format depicted as XXXXXXXX above is 8 hexadecimal
  digits with 0 padding and lower case hexadecimal digits.

  - /sys/bus/pci/slots/XXXXXXXX/power

  In addition to using the FID as the name of the slot, the slot directory
  also contains the following s390-specific slot attributes.

  - uid:
    The User-defined identifier (UID) of the function which may be configured
    by this slot. See also the corresponding attribute of the device.

  A physical function that currently supports a virtual function cannot be
  powered off until all virtual functions are removed with:
  echo 0 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvf

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