** Also affects: ubuntu-power-systems
Importance: Undecided
Status: New
** Changed in: ubuntu-power-systems
Assignee: (unassigned) => Ubuntu on IBM Power Systems Bug Triage
(ubuntu-power-triage)
** Changed in: linux (Ubuntu)
Assignee: Ubuntu on IBM Power Systems Bug Triage (ubuntu-power-triage) =>
(unassigned)
** Changed in: ubuntu-power-systems
Importance: Undecided => High
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https://bugs.launchpad.net/bugs/2056373
Title:
Multiple issues found on Ubuntu 20.04 against HVCS
Status in The Ubuntu-power-systems project:
New
Status in linux package in Ubuntu:
New
Bug description:
---Problem Description---
Issues with HVCS and hotplugging issues.
When working on Canonical bug 2023243, it was discovered that mkvterm
was not working for multiple reasons. This bug will cover the issues
found in HVCS, and hotplugging issues found when drmgr writes the slot
information to .../add_slot.
When mkvterm is ran, it ultimately fails because it calls pvmutil which
fails. pvmutil calls drmgr, and drmgr is adding a slot correctly. However, when
drmgr writes the slot information to ?/add_slot, the return is -ENODEV. This
leads to HVCS never having probe() called. In addition, HVCS is missing
patches, and is broken without them. 8 kernel patches have been identified to
fix these issues.
---uname output---
Linux neop91.pok.stglabs.ibm.com 5.4.0-173-generic #191-Ubuntu SMP Fri Feb 2
13:54:35 UTC 2024 ppc64le ppc64le ppc64le GNU/Linux
---Steps to Reproduce---
Run mkvterm with an id. mkvterm will fail because /dev/hvcs* device nodes
are missing. See
https://bugs.launchpad.net/ubuntu/+source/powerpc-utils/+bug/2023243 for more
information.
------------------------
2 commits made to arch/powerpc/platforms/pseries/of_helpers.c are
needed. These commits fix the hotplugging issue seen when drmgr goes
to write the slot information to /sys/bus/pci/slots/control/add_slot.
This is also why the HVCS device nodes were not being created, as
mentioned in the previous bug.
The issue lies in rpadlpar_io and rpaphp calling an of helper function
of_read_drc_info_cell(). Without these commits, the value stored
drc_index_start is incorrect. This ultimately results in the entire
SLOT string being incorrect, and rpaphp never finding the newly added
slot by drmgr. rpadlpar then returns -ENODEV. Therefore, HVCS is never
probed, and the device nodes are never created.
Ideally - HVCS, rpadlpar_io, and rpaphp should not even need to be
loaded prior to drmgr adding a vio slot. If rpadlpar_io and rpaphp are
not loaded, drmgr will load them. In addition, if rpadlpar_io and
rpaphp register the new slot correctly, rpadlpar_io will call
dlpar_add_vio_slot(), which calls vio_register_device_node() with the
device node. This is what tells the driver core to init and probe HVCS
(which is needed to create the device nodes).
In addition to the 2 commits mentioned above, 6 HVCS commits are
needed. HVCS is essentially broken without them. Issues include race
conditions, hotplug remove issues, as well as memory leaks. These
commits have been added to other distros after multiple issues were
seen. Without these commits, 20.04 will experience the same issues.
IBM plans on stress testing these changes after an updated kernel is
provided in focal-proposed.
-------
2 commits that make changes to
arch/powerpc/platforms/pseries/of_helpers.c:
powerpc/pseries: Fix bad drc_index_start value parsing of drc-info entry
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=57409d4fb12c185b2c0689e0496878c8f6bb5b58
powerpc/pseries: Fix of_read_drc_info_cell() to point at next record
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=c5e76fa05b2df519b9f08571cc57e623c1569faa
HVCS commits:
hvcs: Fix hvcs port reference counting
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=6a9a733edd46732e906d976dc21a42dd361e53cc
hvcs: Use dev_groups to manage hvcs device attributes
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=760aa5e81f33e0da82512c4288489739a6d1c556
hvcs: Use driver groups to manage driver attributes
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=503a90dd619d52dcac2cc68bd742aa914c7cd47a
hvcs: Get reference to tty in remove
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=3a8d3b366ce47024bf274eac783f8af5df2780f5
hvcs: Use vhangup in hotplug remove
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=d432228bc7b1b3f0ed06510278ff5a77b3749fe6
hvcs: Synchronize hotplug remove with port free
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=28d49f8cbe9c7966f91ee1b5ec2f997f6e55bf9f
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