尽管使用了性能调节器，但处理器频率仍保持在最低水平。内核和硬件在频率上不一致？

Question

我在 Linux (Ubuntu 18.04) 上使用带有四个处理器内核的 MacBook Retina：

$ grep -E '^model name|^cpu MHz' /proc/cpuinfo
model name  : Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz
cpu MHz     : 799.976
model name  : Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz
cpu MHz     : 799.993
model name  : Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz
cpu MHz     : 799.992
model name  : Intel(R) Core(TM) i5-4258U CPU @ 2.40GHz
cpu MHz     : 800.016

为了启用这个调控器（和按需调控器），我切换到acpi-cpufreq驱动程序。按照（将 CPU 调节器设置为按需或保守）和（https://ubuntuforums.org/showthread.php?t=1767485）中的说明，我必须在以下位置启用两个内核标志grub.cfg：

intel_pstate=disable processor.ignore_ppc=1

反正。这就是cpufreq-info给我的：

  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 3
  CPUs which need to have their frequency coordinated by software: 3
  maximum transition latency: 10.0 us.
  hardware limits: 768 MHz - 2.40 GHz
  available frequency steps: 2.40 GHz, 2.40 GHz, 2.30 GHz, 2.00 GHz, 1.80 GHz, 1.50 GHz, 1.30 GHz, 1.10 GHz, 900 MHz, 768 MHz
  available cpufreq governors: conservative, ondemand, userspace, powersave, performance, schedutil
  current policy: frequency should be within 768 MHz and 2.40 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 800 MHz.

所以 768-2400MHz 硬件限制是众所周知的，但不知何故它拒绝远离 800MHz。我尝试了 on demand 但没有成功。

现在是有趣的部分。如果我只是使用cpupower frequency-info，我会得到

  current CPU frequency: Unable to call hardware
  current CPU frequency: 800 MHz (asserted by call to kernel)

但是，如果我cpupower以 root 身份调用，我会得到

  current CPU frequency: 2.40 GHz (asserted by call to hardware)

这怎么可能？内核和硬件报告不同的值（感觉很慢，所以我相信内核）。您对这里可能出现的问题有任何线索吗？