1.. SPDX-License-Identifier: GPL-2.0 2 3========= 4S/390 PCI 5========= 6 7Authors: 8 - Pierre Morel 9 10Copyright, IBM Corp. 2020 11 12 13Command line parameters and debugfs entries 14=========================================== 15 16Command line parameters 17----------------------- 18 19* nomio 20 21 Do not use PCI Mapped I/O (MIO) instructions. 22 23* norid 24 25 Ignore the RID field and force use of one PCI domain per PCI function. 26 27debugfs entries 28--------------- 29 30The S/390 debug feature (s390dbf) generates views to hold various debug results in sysfs directories of the form: 31 32 * /sys/kernel/debug/s390dbf/pci_*/ 33 34For example: 35 36 - /sys/kernel/debug/s390dbf/pci_msg/sprintf 37 Holds messages from the processing of PCI events, like machine check handling 38 and setting of global functionality, like UID checking. 39 40 Change the level of logging to be more or less verbose by piping 41 a number between 0 and 6 to /sys/kernel/debug/s390dbf/pci_*/level. For 42 details, see the documentation on the S/390 debug feature at 43 Documentation/arch/s390/s390dbf.rst. 44 45Sysfs entries 46============= 47 48Entries specific to zPCI functions and entries that hold zPCI information. 49 50* /sys/bus/pci/slots/XXXXXXXX 51 52 The slot entries are set up using the function identifier (FID) of the 53 PCI function. The format depicted as XXXXXXXX above is 8 hexadecimal digits 54 with 0 padding and lower case hexadecimal digits. 55 56 - /sys/bus/pci/slots/XXXXXXXX/power 57 58 A physical function that currently supports a virtual function cannot be 59 powered off until all virtual functions are removed with: 60 echo 0 > /sys/bus/pci/devices/XXXX:XX:XX.X/sriov_numvf 61 62* /sys/bus/pci/devices/XXXX:XX:XX.X/ 63 64 - function_id 65 A zPCI function identifier that uniquely identifies the function in the Z server. 66 67 - function_handle 68 Low-level identifier used for a configured PCI function. 69 It might be useful for debugging. 70 71 - pchid 72 Model-dependent location of the I/O adapter. 73 74 - pfgid 75 PCI function group ID, functions that share identical functionality 76 use a common identifier. 77 A PCI group defines interrupts, IOMMU, IOTLB, and DMA specifics. 78 79 - vfn 80 The virtual function number, from 1 to N for virtual functions, 81 0 for physical functions. 82 83 - pft 84 The PCI function type 85 86 - port 87 The port corresponds to the physical port the function is attached to. 88 It also gives an indication of the physical function a virtual function 89 is attached to. 90 91 - uid 92 The user identifier (UID) may be defined as part of the machine 93 configuration or the z/VM or KVM guest configuration. If the accompanying 94 uid_is_unique attribute is 1 the platform guarantees that the UID is unique 95 within that instance and no devices with the same UID can be attached 96 during the lifetime of the system. 97 98 - uid_is_unique 99 Indicates whether the user identifier (UID) is guaranteed to be and remain 100 unique within this Linux instance. 101 102 - pfip/segmentX 103 The segments determine the isolation of a function. 104 They correspond to the physical path to the function. 105 The more the segments are different, the more the functions are isolated. 106 107Enumeration and hotplug 108======================= 109 110The PCI address consists of four parts: domain, bus, device and function, 111and is of this form: DDDD:BB:dd.f 112 113* When not using multi-functions (norid is set, or the firmware does not 114 support multi-functions): 115 116 - There is only one function per domain. 117 118 - The domain is set from the zPCI function's UID as defined during the 119 LPAR creation. 120 121* When using multi-functions (norid parameter is not set), 122 zPCI functions are addressed differently: 123 124 - There is still only one bus per domain. 125 126 - There can be up to 256 functions per bus. 127 128 - The domain part of the address of all functions for 129 a multi-Function device is set from the zPCI function's UID as defined 130 in the LPAR creation for the function zero. 131 132 - New functions will only be ready for use after the function zero 133 (the function with devfn 0) has been enumerated. 134