------- Comment From [email protected] 2020-05-20 09:57 EDT-------
As with other architectures, we must be able to verify the following
relationships between PFs and VFs for proper management (including by libvirt)
of network interfaces:
1. Determine if a device is a virtual function: for other architectures this is
currently available in the file `physfn` which is a link to the parent PF's
device.
2. Determine virtual functions of a physical function: for other architectures
this is currently available as `virtfn{index}` links under the PF device's
directory.
3. Determine the physical function of a virtual function: on x86 this is
currently available in the file `physfn` which is a link to the parent PF
More details for the already existing parameters mentioned above can be
found here: https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-
bus-pci
Moreover creating not just the sysfs but also the in-kernel link
(struct pci_dev->physfn) also allows us to use the common code path
for disabling/shutdown of PFs.
This code path is currently fenced off by the
struct pci_dev->no_vf_scan flag of which s390 is currently the only user.
This in turn allows for a graceful and orderly shutdown of VFs
associated with a VF as triggered by:
echo 0 > /sys/bus/pci/devices/<some_pf>/sriov_numvfs
Previously this could leave the card in an unresponsive error state.
The patches for this have been discussed and Acked-by the
responsible upstream maintainer here:
https://lore.kernel.org/linux-pci/[email protected]/
They are currently queued to be posted to the public s390 Kernel
repository and linux-next / 5.8.
These depend on the previous multi-function/enumeration rework.
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https://bugs.launchpad.net/bugs/1879704
Title:
[UBUNTU 20.04] s390x/pci: implement linking between PF and VF for
multifunction devices
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