GitLab

So the reserve_ebda_region() code has accumulated a number of
problems over the years that make it really difficult to read
and understand:

- The calculation of 'lowmem' and 'ebda_addr' is an unnecessarily
  interleaved mess of first lowmem, then ebda_addr, then lowmem tweaks...

- 'lowmem' here means 'super low mem' - i.e. 16-bit addressable memory. In other
  parts of the x86 code 'lowmem' means 32-bit addressable memory... This makes it
  super confusing to read.

- It does not help at all that we have various memory range markers, half of which
  are 'start of range', half of which are 'end of range' - but this crucial
  property is not obvious in the naming at all ... gave me a headache trying to
  understand all this.

- Also, the 'ebda_addr' name sucks: it highlights that it's an address (which is
  obvious, all values here are addresses!), while it does not highlight that it's
  the _start_ of the EBDA region ...

- 'BIOS_LOWMEM_KIL...