Commit de267a7c authored by Pierre Morel's avatar Pierre Morel Committed by Vasily Gorbik
Browse files

s390/pci: Documentation for zPCI 



There are changes in the usage of PCI for the user:
 - new kernel parameter
 - modification of the way functions are enumerated

Let's document these.

Signed-off-by: default avatarPierre Morel <pmorel@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 53dd462a

Documentation/admin-guide/kernel-parameters.txt

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				may put more devices in an IOMMU group.

		force_floating	[S390] Force usage of floating interrupts.

		nomio		[S390] Do not use MIO instructions.

		norid		[S390] ignore the RID field and force use of

				one PCI domain per PCI function



	pcie_aspm=	[PCIE] Forcibly enable or disable PCIe Active State Power

			Management.

Documentation/s390/index.rst

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@@ -15,6 +15,7 @@ s390 Architecture 
    vfio-ccw

    zfcpdump

    common_io

    pci



    text_files

Documentation/s390/pci.rst

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.. SPDX-License-Identifier: GPL-2.0



=========

S/390 PCI

=========



Authors:

        - Pierre Morel



Copyright, IBM Corp. 2020





command line parameters and debugfs entries

===========================================



Command line parameters

-----------------------



* nomio



  Do not use MIO instructions.



* norid



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



debugfs entries

---------------



* /sys/kernel/debug/s390dbf/pci_*/ (S/390 debug feature)



  Some views generated by the debug feature to hold various debug outputs.



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

    Messages from the processing of PCI events like machine check handling

    and setting of global functionality like UID checking.



  The level of logging can be changed to be more or less verbose by piping to

  /sys/kernel/debug/s390dbf/pci_*/level a number between 0 and 6; see the

  documentation on the S/390 debug feature (Documentation/s390/s390dbf.rst)

  for details.



Sysfs entries

=============



Specific entries, or entries specificities for zPCI functions.



* /sys/bus/pci/slots/XXXXXXXX



  The slot entries are setup using the FID (Function Identifier) of the

  PCI function.



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



  A physical function currently supporting virtual function can not be

  powered-off until all virtual-function have been removed with

  echo 0 > /sys/bus/pci/devices/XXXX:XX:XX.X/sriov_numvf



* /sys/bus/pci/devices/XXXX:XX:XX.X/



  - function_id

    zPCI function identifier unique for the complete Z System.

    It define uniquely a function in the system.



  - function_handle

    Low level identifier used for a configured PCI function.

    It may be useful for debuging.



  - pchid

    Model dependent location of the I/O adapter.



  - pfgid

    PCI Function Group ID, functions sharing identical functionality

    are using a common identifier.

    A PCI group defines interrupts, IOMMU, IOTLB and DMA specifics.



  - vfn

    The Virtual Function Number, from 1 to N for virtual functions.

    0 for physical functions.



  - pft

    PCI function type specifies the type of the PCI function.



  - port

    The port correspond to the physical port the function is attached to.

    It also gives an indication on the physical function a virtual function

    is attached to.



  - uid

    The UID, Unique Identifier is defined when configuring a LPAR and is

    unique inside an LPAR.



  - pfip/segmentX

    The segments are used to determine the isolation of a function.

    They corresponds to the physical path to the function.

    The more the segment are different the more the functions are isolated.



Enumeration and hotplug

=======================



The PCI address is made of 4 parts: domain, bus, device and function,

like in DDDD:BB:dd.f



* When not using multi-functions (norid is set or firmware does not support

  multi-functions)



  - There is only one function per domain.



  - the domain is set from the zPCI function's UID as defined during the

    LPAR creation.



  - Addresses look like DDDD:00:00.0



* When using multi-functions (norid parameter is not set), there are some

  change in the way zPCI functions are addressed:



  - There is still only one bus per domain.



  - There can be up to 256 functions per bus.



  - The domain part of the address of all functions of all functions for

    a multi-Function device is set from the zPCI function's UID as defined

    in the LPAR creation for the function zero.



  - New functions will only be ready to be used after the function zero

    (the function with devfn 0) has been enumerated.

MAINTAINERS

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@@ -14662,6 +14662,7 @@ S: Supported 
W:	http://www.ibm.com/developerworks/linux/linux390/

F:	arch/s390/pci/

F:	drivers/pci/hotplug/s390_pci_hpc.c

F:	Documentation/s390/pci.rst









S390 VFIO AP DRIVER









M:	Tony Krowiak <akrowiak@linux.ibm.com>