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

[Ingo Molnar]

* Dave Hansen <dave.hansen@xxxxxxxxx> wrote:

> 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?

Isn't it the other way around? MAX_PHYS{MEM,ADDR}_BITS are now *always* 
dynamic, their value depending on whether LA57 is available and used.

Thanks,

	Ingo