Re: [PATCHv3 2/4] x86/64/mm: Make SPARSEMEM_VMEMMAP the only memory model

[Dave Hansen]

On 5/16/25 05:33, Kirill A. Shutemov wrote:
> 5-level paging only supports SPARSEMEM_VMEMMAP. CONFIG_X86_5LEVEL is
> being phased out, making 5-level paging support mandatory.
> 
> Make CONFIG_SPARSEMEM_VMEMMAP mandatory for x86-64 and eliminate
> any associated conditional statements.
I think we have ourselves a catch-22 here.

SPARSEMEM_VMEMMAP was selected because the other sparsemem modes
couldn't handle a dynamic MAX_PHYS{MEM,ADDR}_BITS introduced by 5-level
paging. Now you're proposing making it static again, but keeping the
SPARSEMEM_VMEMMAP dependency.

If you remove the dynamic MAX_PHYS{MEM,ADDR}_BITS, you should also
remove the dependency on SPARSEMEM_VMEMMAP. No?