riscv32 EXT4 splat, 6.8 regression?

[Matthew Wilcox]

On Tue, Apr 16, 2024 at 07:19:27PM +0300, Mike Rapoport wrote:
> > "last page of the first gigabyte" - why first gigabyte? Do you mean
> > last page of *last* gigabyte?
>  
> With 3G-1G split linear map can map only 1G from 0xc0000000 to 0xffffffff
> (or 0x00000000 with 32-bit overflow):
> 
> [    0.000000]       lowmem : 0xc0000000 - 0x00000000   (1024 MB)

... but you can't map that much.  You need to reserve space for (may not
be exhaustive):

 - PCI BARs (or other MMIO)
 - vmap
 - kmap
 - percpu
 - ioremap
 - modules
 - fixmap
 - Maybe EFI runtime services?

You'll be lucky to get 800MB of ZONE_NORMAL.