Re: [PATCH] arm64: mm: Use generic enum pgtable_level

[Kevin Brodsky]

On 16/03/2026 15:22, Ryan Roberts wrote:
>>  static phys_addr_t __pgd_pgtable_alloc(struct mm_struct *mm, gfp_t gfp,
>> -				       enum pgtable_type pgtable_type)
>> +				       enum pgtable_level pgtable_level)
>>  {
>>  	/* Page is zeroed by init_clear_pgtable() so don't duplicate effort. */
>>  	struct ptdesc *ptdesc = pagetable_alloc(gfp & ~__GFP_ZERO, 0);
>> @@ -539,40 +539,42 @@ static phys_addr_t __pgd_pgtable_alloc(struct mm_struct *mm, gfp_t gfp,
>>  
>>  	pa = page_to_phys(ptdesc_page(ptdesc));
>>  
>> -	switch (pgtable_type) {
>> -	case TABLE_PTE:
>> +	switch (pgtable_level) {
>> +	case PGTABLE_LEVEL_PTE:
>>  		BUG_ON(!pagetable_pte_ctor(mm, ptdesc));
>>  		break;
>> -	case TABLE_PMD:
>> +	case PGTABLE_LEVEL_PMD:
>>  		BUG_ON(!pagetable_pmd_ctor(mm, ptdesc));
>>  		break;
>> -	case TABLE_PUD:
>> +	case PGTABLE_LEVEL_PUD:
>>  		pagetable_pud_ctor(ptdesc);
>>  		break;
>> -	case TABLE_P4D:
>> +	case PGTABLE_LEVEL_P4D:
>>  		pagetable_p4d_ctor(ptdesc);
>>  		break;
>> +	default:
>> +		break;
> nit: I think we should either explicitly support pgd or explicitly bug/warn. Now
> that the enum has PGTABLE_LEVEL_PGD it looks legit to call __pgd_pgtable_alloc()
> to allocate one. But it will currently silently fail to call pagetable_pgd_ctor().

I hesitated there as well, eventually I concluded that we're dealing
with kernel page tables so we'll never allocate a PGD anyway...

> Probably simplest just to call BUG() in the default path?

... but that's certainly fine by me :)

> With this addressed:
>
> Reviewed-by: Ryan Roberts <ryan.roberts@xxxxxxx>

Thanks!

- Kevin