Public bug reported:

CONFIG_LOG_BUF_SHIFT
policy<{
'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
        help
          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.

          Examples:
                     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.

** Affects: linux (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1824863

Title:
  CONFIG_LOG_BUF_SHIFT is too low on arm64

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