[Bug 1876018] Re: 40-vm-hotadd.rules attempts to set non-existent sysfs parameters

[Dan Streetman]

> Apr 29 22:36:46 focal01 systemd-udevd[266]: memory7:
/usr/lib/udev/rules.d/40-vm-hotadd.rules:9 Failed to write
ATTR{/sys/devices/system/memory/memory7/state}, ignoring: Invalid
argument

This isn't because the file doesn't exist, because the udev rule checks
for its existence before trying to write to it.  The error is because
the kernel is rejecting the write to its state file for some reason.  In
a really quick test, it seems like this is because it's already online;
the kernel default has been CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE=y since
at least 4.15.

I think the error message is harmless, since the memory is already
online, but the udev rule should be fixed to check if it's offline
before actually trying to online it.

Can you test with the systemd from this ppa to see if the error message is gone?
https://launchpad.net/~ddstreet/+archive/ubuntu/lp1876018

Also please make sure all your memory and cpus are online after
booting/hotadding.

Note that I might just remove this rule entirely, since it really
shouldn't be needed anymore, now that the kernel default is to online
hotplugged cpus/memory, but I want to verify that first.

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https://bugs.launchpad.net/bugs/1876018

Title:
  40-vm-hotadd.rules attempts to set non-existent sysfs parameters

Status in systemd package in Ubuntu:
  New

Bug description:
  In focal, udev's 40-vm-hotadd.rules (from debian/extra/rules-ubuntu)
  tries to write to invalid (as of 5.4.0-1010-azure) sysfs nodes
  resulting in warnings such as:

  Apr 29 22:36:46 focal01 systemd-udevd[266]: memory7:
  /usr/lib/udev/rules.d/40-vm-hotadd.rules:9 Failed to write
  ATTR{/sys/devices/system/memory/memory7/state}, ignoring: Invalid
  argument

  Perhaps 40-vm-hotadd.rules needs to be updated for 5.4 semantics,
  removed, or something else. This behavior is present on systems
  upgraded from 18.04 (via d-r-u) as well as new focal systems, upon
  first reboot of the VM.

  udev: 245.4-4ubuntu3

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