[Bug 1987541] Re: shim executes GRUB w/ dirty instruction cache on arm64

[Launchpad Bug Tracker]

** Merge proposal linked:
   https://code.launchpad.net/~juliank/shim/+git/shim-signed/+merge/436050

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https://bugs.launchpad.net/bugs/1987541

Title:
  shim executes GRUB w/ dirty instruction cache on arm64

Status in shim package in Ubuntu:
  In Progress

Bug description:
  [Impact]
  On arm64 platforms, GRUB may occasionally crash after being executed by shim. We're seeing it on the order of 1/100 boots.

  [Test Case]
  Put an arm64 server in a reboot loop. We're seeing this w/ a Cortex A72-based system (Nvidia Bluefield).

  [Fix]
  https://github.com/rhboot/shim/commit/5c537b3d0cf8c393dad2e61d49aade68f3af1401

  [What could go wrong]
  The only negative here would seem to be the performance impact of flushing the cache, which is unlikely to be noticeable.

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