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On s390 each PCI device has a user-defined ID (UID) exposed under
/sys/bus/pci/devices/<dev>/uid. This ID was designed to serve as the PCI
device's primary index and to match the device within Linux to the
device configured in the hypervisor. To serve as a primary identifier
the UID must be unique within the Linux instance, this is guaranteed by
the platform if and only if the UID Uniqueness Checking flag is set
within the CLP List PCI Functions response.
While the UID has been exposed to userspace since commit ac4995b9d5
("s390/pci: add some new arch specific pci attributes") whether or not
the platform guarantees its uniqueness for the lifetime of the Linux
instance while defined is not visible from userspace. Remedy this by
exposing this as a per device attribute at
/sys/bus/pci/devices/<dev>/uid_is_unique
Keeping this a per device attribute allows for maximum flexibility if we
ever end up with some devices not having a UID or not enjoying the
guaranteed uniqueness.
Signed-off-by: Niklas Schnelle <schnelle@linux.ibm.com>
Reviewed-by: Viktor Mihajlovski <mihajlov@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
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 digitis.
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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 debuging.
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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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