[libvirt PATCH 0/1] Add a PCI/PCIe device VPD Capability

Dmitrii Shcherbakov dmitrii.shcherbakov at canonical.com
Tue Aug 24 14:05:54 UTC 2021

Add support for deserializing the binary PCI/PCIe VPD format and
exposing VPD resources as XML elements in a new nested capability
of PCI/PCIe devices called 'vpd'.

The VPD format is specified in "I.3. VPD Definitions" in PCI specs
(2.2+) and "6.28.1 VPD Format" PCIe 4.0. As section 6.28 in PCIe 4.0
notes, the PCI Local Bus and PCIe VPD formats are binary compatible
and PCIe 4.0 merely started incorporating what was already present in
PCI specs.

Linux kernel exposes a binary blob in the VPD format via sysfs since
v2.6.26 (commit 94e6108803469a37ee1e3c92dafdd1d59298602f) which requires
a parser to interpret.

There are usage scenarios where information such as the board serial
number needs to be retrieved from PCI(e) VPD. Projects like Nova can
utilize this information for cases which involve virtual interface
plugging on SmartNIC DPUs but there may be other scenarios and types of
information useful to retrieve from VPD. The fact that the format is
binary requires proper parsing instead of substring searching hence the
full parser is proposed. Likewise, checksum validation requires proper
parsing as well.

The patch follows a prior discussion on the mailing list which has
additional context about the use-case but a narrower proposal:


The new functionality is mostly contained in virpcivpd with a
couple of new functions added to virpci. Additionally, the necessary XML
serialization/deserialization and glue code is added to expose the VPD
capability to external clients as XML.

A new capability flag is added along with a new capability in order to
allow for filtering of PCI devices with the VPD capability using virsh:

virsh nodedev-list --cap vpd
sudo virsh nodedev-dumpxml --device pci_dddd_bb_ss_f

In this example having the root uid is required in order to access the
vpd sysfs entry, therefore, the nodedev XML output will only contain
the VPD capability if virsh is run as root.

The capability is treated as dynamic due to the presence of read-write
sections in the VPD format per PCI/PCIe specs (the idea being that
read-write resource fields may potentially be altered by the DPU OS
over time independently from the host OS).

Unit tests cover the parser functionality (including many possible
invalid cases), in-memory representation as well as XML serialization
and deserialization.

Manual functional testing was performed with 2 DPUs and several other
NIC models which expose PCI(e) VPD. Testing have also been performed
for devices that do not have VPD or those that expose a VPD capability
but exhibit invalid behavior (I/O errors while reading a sysfs entry).

Per the existing guidelines, the implementation relies heavily on glib
for various purposes.


Dmitrii Shcherbakov (1):
  Add a PCI/PCIe device VPD Capability

 build-aux/syntax-check.mk                     |   4 +-
 docs/drvnodedev.html.in                       |  46 ++
 docs/formatnode.html.in                       |  24 +-
 docs/schemas/nodedev.rng                      |  40 +
 include/libvirt/libvirt-nodedev.h             |   1 +
 po/POTFILES.in                                |   1 +
 src/conf/node_device_conf.c                   | 258 ++++++
 src/conf/node_device_conf.h                   |   6 +-
 src/conf/virnodedeviceobj.c                   |   7 +-
 src/libvirt_private.syms                      |  17 +
 src/node_device/node_device_driver.c          |   2 +
 src/node_device/node_device_udev.c            |   2 +
 src/util/meson.build                          |   1 +
 src/util/virpci.c                             |  60 ++
 src/util/virpci.h                             |   3 +
 src/util/virpcivpd.c                          | 771 +++++++++++++++++
 src/util/virpcivpd.h                          | 106 +++
 src/util/virpcivpdpriv.h                      |  42 +
 tests/meson.build                             |   1 +
 .../pci_0000_42_00_0_vpd.xml                  |  33 +
 .../pci_0000_42_00_0_vpd.xml                  |   1 +
 tests/nodedevxml2xmltest.c                    |   1 +
 tests/testutils.c                             |  51 ++
 tests/testutils.h                             |   6 +
 tests/virpcitest.c                            |   3 +
 tests/virpcivpdtest.c                         | 777 ++++++++++++++++++
 tools/virsh-nodedev.c                         |   3 +
 27 files changed, 2262 insertions(+), 5 deletions(-)
 create mode 100644 src/util/virpcivpd.c
 create mode 100644 src/util/virpcivpd.h
 create mode 100644 src/util/virpcivpdpriv.h
 create mode 100644 tests/nodedevschemadata/pci_0000_42_00_0_vpd.xml
 create mode 120000 tests/nodedevxml2xmlout/pci_0000_42_00_0_vpd.xml
 create mode 100644 tests/virpcivpdtest.c


More information about the libvir-list mailing list