RE: [PATCH v2] x86: Use low memory size directly from Multiboot

[<dinhngoc.tu@xxxxxxx>]

> -----Original Message-----
> From: Jan Beulich <jbeulich@xxxxxxxx>
> Sent: Wednesday, 9 February 2022 16:23
> To: dinhngoc.tu@xxxxxxx
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx
> Subject: Re: [PATCH v2] x86: Use low memory size directly from Multiboot
> 
> On 09.02.2022 16:20, dinhngoc.tu@xxxxxxx wrote:
> > This change should only affect the particular case of booting with
> Multiboot2 without EFI (e.g. legacy BIOS or Kexec). Other cases like
> Multiboot 0.x, EFI booting (with or without MB2), or bootloaders that
> generate the BASIC_MEMINFO tag correctly shouldn't be affected.
> 
> How that? You're taking out the reading of the BDA value altogether, aren't
> you? This is certainly a change affecting other environments as well.
> 
> Jan

I missed that the BDA was used when booting on Multiboot 0.x as well. I can add 
a fallback to use the BDA when the bootloader doesn't provide low memory size 
in the MBI.