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

[Dan Streetman]

** Description changed:

+ [impact]
+ 
+ 40-vm-hotadd.rules unconditionally tries onlining memory, which results
+ in logged error messages if the memory is already online
+ 
+ [test case]
+ 
+ since this rules file restricts operation to only hyper-v or xen guests,
+ boot a hyper-v or xen vm guest, and check for logged error msgs like:
+ 
+ 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
+ 
+ alternately, to test on a vm guest other than hyper-v or xen,
+ comment/remove the 'GOTO="vm_hotadd_end"' line from the rules file and
+ reboot.
+ 
+ [regression potential]
+ 
+ as this adds a check before attempting to online memory for hyper-v and
+ xen vm guests, any regression would likely involve failure to correctly
+ online all memory on those guest platforms.
+ 
+ [scope]
+ 
+ this rule has been around for a long time, so is needed for x/b/f/g.
+ 
+ [original 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

** Also affects: systemd (Ubuntu Bionic)
   Importance: Undecided
       Status: New

** Also affects: systemd (Ubuntu Xenial)
   Importance: Undecided
       Status: New

** Changed in: systemd (Ubuntu Xenial)
       Status: New => In Progress

** Changed in: systemd (Ubuntu Bionic)
       Status: New => In Progress

** Changed in: systemd (Ubuntu Focal)
   Importance: Undecided => Medium

** Changed in: systemd (Ubuntu Bionic)
   Importance: Undecided => Medium

** Changed in: systemd (Ubuntu Xenial)
   Importance: Undecided => Medium

** Changed in: systemd (Ubuntu Focal)
     Assignee: (unassigned) => Dan Streetman (ddstreet)

** Changed in: systemd (Ubuntu Xenial)
     Assignee: (unassigned) => Dan Streetman (ddstreet)

** Changed in: systemd (Ubuntu Focal)
       Status: New => In Progress

** Changed in: systemd (Ubuntu Bionic)
     Assignee: (unassigned) => Dan Streetman (ddstreet)

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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:
  Fix Released
Status in systemd source package in Xenial:
  In Progress
Status in systemd source package in Bionic:
  In Progress
Status in systemd source package in Focal:
  In Progress

Bug description:
  [impact]

  40-vm-hotadd.rules unconditionally tries onlining memory, which
  results in logged error messages if the memory is already online

  [test case]

  since this rules file restricts operation to only hyper-v or xen
  guests, boot a hyper-v or xen vm guest, and check for logged error
  msgs like:

  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

  alternately, to test on a vm guest other than hyper-v or xen,
  comment/remove the 'GOTO="vm_hotadd_end"' line from the rules file and
  reboot.

  [regression potential]

  as this adds a check before attempting to online memory for hyper-v
  and xen vm guests, any regression would likely involve failure to
  correctly online all memory on those guest platforms.

  [scope]

  this rule has been around for a long time, so is needed for x/b/f/g.

  [original 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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