[{"id":3674204,"web_url":"http://patchwork.ozlabs.org/comment/3674204/","msgid":"<15f9e61239cd8f8b09bb0f058848e80070c0b1de.camel@linux.ibm.com>","list_archive_url":null,"date":"2026-04-07T14:09:33","subject":"Re: [PATCH v8 1/2] docs: s390/pci: Improve and update PCI\n documentation","submitter":{"id":85804,"url":"http://patchwork.ozlabs.org/api/people/85804/","name":"Gerd Bayer","email":"gbayer@linux.ibm.com"},"content":"On Tue, 2026-04-07 at 15:24 +0200, Niklas Schnelle wrote:\n> Update the s390 specific PCI documentation to better reflect current\n> behavior and terms such as the handling of Isolated VFs via commit\n> 25f39d3dcb48 (\"s390/pci: Ignore RID for isolated VFs\").\n> \n> Add a descriptions for /sys/firmware/clp/uid_checking which was added\n> in commit b043a81ce3ee (\"s390/pci: Expose firmware provided UID Checking\n> state in sysfs\") but missed documentation.\n> \n> Similarly add documentation for the fidparm attribute added by commit\n> 99ad39306a62 (\"s390/pci: Expose FIDPARM attribute in sysfs\") and\n> add a list of pft values and their names.\n> \n> Finally improve formatting of the different attribute descriptions by\n> adding a separating colon.\n> \n> Reviewed-by: Farhan Ali \n> Acked-by: Randy Dunlap \n> Tested-by: Randy Dunlap \n> Reviewed-by: Matthew Rosato \n> Signed-off-by: Niklas Schnelle \n> ---\n> Documentation/arch/s390/pci.rst | 144 +++++++++++++++++++++++++++-------------\n> 1 file changed, 97 insertions(+), 47 deletions(-)\n> \n> diff --git a/Documentation/arch/s390/pci.rst b/Documentation/arch/s390/pci.rst\n> index d5755484d8e75c7bf67a350e61bbe04f0452a2fa..c3476de4f03278d07099aa32cbea0f868b6e9c9c 100644\n> --- a/Documentation/arch/s390/pci.rst\n> +++ b/Documentation/arch/s390/pci.rst\n> @@ -6,6 +6,7 @@ S/390 PCI\n> \n> Authors:\n> - Pierre Morel\n> + - Niklas Schnelle\n> \n> Copyright, IBM Corp. 2020\n> \n> @@ -27,14 +28,16 @@ Command line parameters\n> debugfs entries\n> ---------------\n> \n> -The S/390 debug feature (s390dbf) generates views to hold various debug results in sysfs directories of the form:\n> +The S/390 debug feature (s390dbf) generates views to hold various debug results\n> +in sysfs directories of the form:\n> \n> * /sys/kernel/debug/s390dbf/pci_*/\n> \n> For example:\n> \n> - /sys/kernel/debug/s390dbf/pci_msg/sprintf\n> - Holds messages from the processing of PCI events, like machine check handling\n> +\n> + holds messages from the processing of PCI events, like machine check handling\n> and setting of global functionality, like UID checking.\n> \n> Change the level of logging to be more or less verbose by piping\n> @@ -47,87 +50,134 @@ Sysfs entries\n> \n> Entries specific to zPCI functions and entries that hold zPCI information.\n> \n> -* /sys/bus/pci/slots/XXXXXXXX\n> +* /sys/bus/pci/slots/XXXXXXXX:\n> \n> - The slot entries are set up using the function identifier (FID) of the\n> - PCI function. The format depicted as XXXXXXXX above is 8 hexadecimal digits\n> - with 0 padding and lower case hexadecimal digits.\n> + The slot entries are set up using the function identifier (FID) of the PCI\n> + function as slot name. The format depicted as XXXXXXXX above is 8 hexadecimal\n> + digits with 0 padding and lower case hexadecimal digits.\n> \n> - /sys/bus/pci/slots/XXXXXXXX/power\n> \n> A physical function that currently supports a virtual function cannot be\n> powered off until all virtual functions are removed with:\n> - echo 0 > /sys/bus/pci/devices/XXXX:XX:XX.X/sriov_numvf\n> + echo 0 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvf\n> \n> -* /sys/bus/pci/devices/XXXX:XX:XX.X/\n> +* /sys/bus/pci/devices/DDDD:BB:dd.f/:\n> \n> - - function_id\n> - A zPCI function identifier that uniquely identifies the function in the Z server.\n> + - function_id:\n> + The zPCI function identifier (FID) is a 32-bit hexadecimal value that\n> + uniquely identifies the PCI function. Unless the hypervisor provides\n> + a virtual FID e.g. on KVM this identifier is unique across the machine even\n> + between different partitions.\n> \n> - - function_handle\n> - Low-level identifier used for a configured PCI function.\n> - It might be useful for debugging.\n> + - function_handle:\n> + This 32-bit hexadecimal value is a low-level identifier used for a PCI\n> + function. Note that the function handle may be changed and become invalid\n> + on PCI events and when enabling/disabling the PCI function.\n> \n> - - pchid\n> - Model-dependent location of the I/O adapter.\n> + - pchid:\n> + This 16-bit hexadecimal value encodes a model-dependent location for\n> + the PCI function.\n> \n> - - pfgid\n> - PCI function group ID, functions that share identical functionality\n> + - pfgid:\n> + PCI function group ID; functions that share identical functionality\n> use a common identifier.\n> A PCI group defines interrupts, IOMMU, IOTLB, and DMA specifics.\n> \n> - - vfn\n> + - vfn:\n> The virtual function number, from 1 to N for virtual functions,\n> 0 for physical functions.\n> \n> - - pft\n> - The PCI function type\n> + - pft:\n> + The PCI function type is an s390-specific type attribute. It indicates\n> + a more general, usage oriented, type than PCI Specification\n> + class/vendor/device identifiers. That is PCI functions with the same pft\n> + value may be backed by different hardware implementations. At the same time\n> + apart from unclassified functions (pft is 0x00) the same pft value\n> + generally implies a similar usage model. At the same time the same\n> + PCI hardware device may appear with different pft values when in a\n> + different usage model. For example NETD and NETH VFs may be implemented\n> + by the same PCI hardware device but in NETD the parent Physical Function\n> + is user managed while with NETH it is platform managed.\n> \n> - - port\n> - The port corresponds to the physical port the function is attached to.\n> - It also gives an indication of the physical function a virtual function\n> - is attached to.\n> + Currently the following PFT values are defined:\n> \n> - - uid\n> - The user identifier (UID) may be defined as part of the machine\n> - configuration or the z/VM or KVM guest configuration. If the accompanying\n> - uid_is_unique attribute is 1 the platform guarantees that the UID is unique\n> - within that instance and no devices with the same UID can be attached\n> - during the lifetime of the system.\n> + - 0x00 (UNC): Unclassified\n> + - 0x02 (ROCE): RoCE Express\n> + - 0x05 (ISM): Internal Shared Memory\n> + - 0x0a (ROC2): RoCE Express 2\n> + - 0x0b (NVMe): NVMe\n> + - 0x0c (NETH): Network Express hybrid\n> + - 0x0d (CNW): Cloud Network Adapter\n> + - 0x0f (NETD): Network Express direct\n> \n> - - uid_is_unique\n> - Indicates whether the user identifier (UID) is guaranteed to be and remain\n> - unique within this Linux instance.\n> + - port:\n> + The port is a decimal value corresponding to the physical port the function\n> + is attached to. Virtual Functions (VFs) share the port with their parent\n> + Physical Function (PF). A value of 0 indicates that the port attribute is\n> + not applicable for that PCI function type.\n> \n> - - pfip/segmentX\n> + - uid:\n> + The user-defined identifier (UID) for a PCI function is a 32-bit\n> + hexadecimal value. It is defined on a per instance basis as part of the\n> + partition, KVM guest, or z/VM guest configuration. If UID Checking is\n> + enabled the platform ensures that the UID is unique within that instance\n> + and no two PCI functions with the same UID will be visible to the instance.\n> +\n> + Independent of this guarantee and unlike the function ID (FID) the UID may\n> + be the same in different partitions within the same machine. This allows to\n> + create PCI configurations in multiple partitions to be identical in the\n> + UID-namespace.\n> +\n> + - uid_is_unique:\n> + A 0 or 1 flag indicating whether the user-defined identifier (UID) is\n> + guaranteed to be and remain unique within this Linux instance. This\n> + platform feature is called UID Checking.\n> +\n> + - pfip/segmentX:\n> The segments determine the isolation of a function.\n> They correspond to the physical path to the function.\n> The more the segments are different, the more the functions are isolated.\n> \n> + - fidparm:\n> + Contains an 8-bit-per-PCI function parameter field in hexadecimal provided\n> + by the platform. The meaning of this field is PCI function type specific.\n> + For NETH VFs a value of 0x01 indicates that the function supports\n> + promiscuous mode.\n> +\n> +* /sys/firmware/clp/uid_checking:\n> +\n> + In addition to the per-device uid_is_unique attribute this presents a\n> + global indication of whether UID Checking is enabled. This allows users\n> + to check for UID Checking even when no PCI functions are configured.\n> +\n> Enumeration and hotplug\n> =======================\n> \n> The PCI address consists of four parts: domain, bus, device and function,\n> -and is of this form: DDDD:BB:dd.f\n> +and is of this form: DDDD:BB:dd.f.\n> \n> -* When not using multi-functions (norid is set, or the firmware does not\n> - support multi-functions):\n> +* For a PCI function for which the platform does not expose the RID, the\n> + pci=norid kernel parameter is used, or a so-called isolated Virtual Function\n> + which does have RID information but is used without its parent Physical\n> + Function being part of the same PCI configuration:\n> \n> - There is only one function per domain.\n> \n> - - The domain is set from the zPCI function's UID as defined during the\n> - LPAR creation.\n> + - The domain is set from the zPCI function's UID if UID Checking is on;\n> + otherwise the domain ID is generated dynamically and is not stable\n> + across reboots or hot plug.\n> \n> -* When using multi-functions (norid parameter is not set),\n> - zPCI functions are addressed differently:\n> +* For a PCI function for which the platform exposes the RID and which\n> + is not an Isolated Virtual Function:\n> \n> - There is still only one bus per domain.\n> \n> - - There can be up to 256 functions per bus.\n> + - There can be up to 256 PCI functions per bus.\n> \n> - - The domain part of the address of all functions for\n> - a multi-Function device is set from the zPCI function's UID as defined\n> - in the LPAR creation for the function zero.\n> + - The domain part of the address of all functions within the same topology is\n> + that of the configured PCI function with the lowest devfn within that\n> + topology.\n> \n> - - New functions will only be ready for use after the function zero\n> - (the function with devfn 0) has been enumerated.\n> + - Virtual Functions generated by an SR-IOV capable Physical Function only\n> + become visible once SR-IOV is enabled.\n\n\nLGTM!\nReviewed-by: Gerd Bayer ","headers":{"Return-Path":"\n ","X-Original-To":["incoming@patchwork.ozlabs.org","linux-pci@vger.kernel.org"],"Delivered-To":"patchwork-incoming@legolas.ozlabs.org","Authentication-Results":["legolas.ozlabs.org;\n\tdkim=pass (2048-bit key;\n unprotected) header.d=ibm.com header.i=@ibm.com header.a=rsa-sha256\n header.s=pp1 header.b=QxNMOD6E;\n\tdkim-atps=neutral","legolas.ozlabs.org;\n spf=pass (sender SPF authorized) smtp.mailfrom=vger.kernel.org\n (client-ip=172.234.253.10; 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