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** Changed in: linux (Ubuntu)
       Status: New => Incomplete

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  CONFIG_LOG_BUF_SHIFT is too low on arm64

Status in linux package in Ubuntu:

Bug description:
  'amd64'  : '18',
  'arm64'  : '14',
  'armhf'  : '17',
  'i386'   : '17',
  'ppc64el': '17',
  's390x'  : '17'}>

  Please set CONFIG_LOG_BUF_SHIFT to at least 17 on arm64.

  Potentially bump all 64-bit arches to 18 (or higher!) as was done on
  amd64, meaning set 18 on arm64 s390x ppc64el.

  I have a systemd autopkgtest test that asserts that we see Linux
  kernel command line in the dmesg (journalctl -k -b). And it is
  consistently failing on arm64 scalingstack KVM EFI machines with
  messages of "missing 81 kernel messages".

  config LOG_BUF_SHIFT
          int "Kernel log buffer size (16 => 64KB, 17 => 128KB)"
          range 12 25
          default 17
          depends on PRINTK
            Select the minimal kernel log buffer size as a power of 2.
            The final size is affected by LOG_CPU_MAX_BUF_SHIFT config
            parameter, see below. Any higher size also might be forced
            by "log_buf_len" boot parameter.

                       17 => 128 KB
                       16 => 64 KB
                       15 => 32 KB
                       14 => 16 KB
                       13 =>  8 KB
                       12 =>  4 KB

  14 sounds like redictiously low for arm64. given that 17 is default
  across 32-bit arches, and 18 is default on amd64.

  Please backport this to xenial and up.

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