[Bug 1904585] Re: opal-prd: Have a worker process handle page offlining (Fixes "PlatServices: dyndealloc memory_error() failed" is getting reported in error log (opal-prd))

[Łukasz Zemczak]

I'm not entirely happy with the regression potential section, so let me
work a bit on that.

"Hopefully not much" is not a valid regression potential analysis as it
gives us, the SRU team, no insight into what the actual situation is
like. We all have wishful thinking about our changes! This section
requires looking and understanding the code changes, looking at which
parts of the code are modified and doing a though exercise: hmmm, if
this code is changed, what other parts can it affect? Where should we
expect any problems appear, just in case?

Only then we, as the SRU team, can make a decision whether it is safe
enough to go forward with the SRU or not. Also, it gives everyone a
better understanding what additional dogfooding we might want to perform
to minimize regression risk. Lastly, it's also makes easier bisecting
whenever some regression is found later, when trying to identify which
change is responsible.

Another thing that I'm not entirely happy with is the lack of any DEP-3
headers on any of the patches in the actual uploads. Because of that I
don't know where the patches come from, have those been upstreamed?

I will gladly re-visit those once these issues are resolved.

** Changed in: skiboot (Ubuntu Groovy)
       Status: In Progress => Incomplete

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https://bugs.launchpad.net/bugs/1904585

Title:
  opal-prd: Have a worker process handle page offlining (Fixes
  "PlatServices: dyndealloc memory_error() failed" is getting reported
  in error log (opal-prd))

Status in The Ubuntu-power-systems project:
  In Progress
Status in skiboot package in Ubuntu:
  Fix Released
Status in skiboot source package in Xenial:
  In Progress
Status in skiboot source package in Bionic:
  In Progress
Status in skiboot source package in Focal:
  In Progress
Status in skiboot source package in Groovy:
  Incomplete
Status in skiboot source package in Hirsute:
  Fix Released

Bug description:
  [Impact]

  This impacts the opal-prd userspace command from the skiboot package
  The memory_error() hservice interface expects the memory_error() call to
  just accept the offline request and return without actually offlining the
  memory. Currently we will attempt to offline the marked pages before
  returning to HBRT which can result in an excessively long time spent in the memory_error() hservice call which blocks HBRT from processing other
  errors.

  [Test Case]

  Unfortunately due to the specific hardware requirement I wasn't able
  to reproduce this problem and provide a test case for it. However I
  was able to build this package into a ppa and got the IBM team to
  confirm this problem was resolved for groovy focal, bionic, xenial see
  comment #4 and #6

  [What could go wrong]

  Hopefully not much. The initial fix was prepared back in September and
  I would think regression could have been discovered by now.

  
  [Original Description]

  https://github.com/open-
  power/skiboot/commit/8cbd0de88d162e387f11569eee1bdecef8fad2e3

  opal-prd: Have a worker process handle page offlining

  The memory_error() hservice interface expects the memory_error() call to
  just accept the offline request and return without actually offlining the
  memory. Currently we will attempt to offline the marked pages before
  returning to HBRT which can result in an excessively long time spent in the
  memory_error() hservice call which blocks HBRT from processing other
  errors. Fix this by adding a worker process which performs the page
  offlining via the sysfs memory error interfaces.

  Reviewed-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
  Signed-off-by: Oliver O'Halloran <oohall at gmail.com>

  Thanks in advance for your support.

  Machine Type = Power8 and Power9 OPAL systems

  ---Steps to Reproduce---
  * Inject memory error (UE)
  * Verify that opal-prd doesn't return asynchronously to the platform after requesting the memory offlining operation

  Userspace tool common name: opal-prd

  We need this fix for 16.04.x and 18.04.x LTS releases.

  Fix also is needed for 20.04 and 20.10.

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