Re: [PATCH v2 23/34] ARM: mmu64: create alloc_pte()

[Ahmad Fatoum <a.fatoum@pengutronix.de>]

On 17.05.23 11:03, Sascha Hauer wrote:
> This is a preparation for using two level page tables in the PBL.
> To do that we need a way to allocate page tables in PBL. As malloc
> is not available in PBL, implement a function to allocate a page table
> from the area we also place the TTB.
> 
> Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
> ---
>  arch/arm/cpu/mmu_64.c | 20 +++++++++++++++++---
>  1 file changed, 17 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/cpu/mmu_64.c b/arch/arm/cpu/mmu_64.c
> index 55ada960c5..3cc5b14a46 100644
> --- a/arch/arm/cpu/mmu_64.c
> +++ b/arch/arm/cpu/mmu_64.c
> @@ -32,7 +32,20 @@ static void set_table(uint64_t *pt, uint64_t *table_addr)
>  	*pt = val;
>  }
>  
> -static uint64_t *create_table(void)
> +#ifdef __PBL__
> +static uint64_t *alloc_pte(void)
> +{
> +	static unsigned int idx;
> +
> +	idx++;
> +
> +	if (idx * GRANULE_SIZE >= ARM_EARLY_PAGETABLE_SIZE)
> +		return NULL;
> +
> +	return (void *)ttb + idx * GRANULE_SIZE;
> +}
> +#else
> +static uint64_t *alloc_pte(void)
>  {
>  	uint64_t *new_table = xmemalign(GRANULE_SIZE, GRANULE_SIZE);
>  
> @@ -41,6 +54,7 @@ static uint64_t *create_table(void)

Nit: There's a memset(new_table, 0, GRANULE_SIZE); inside here, which doesn't
exist in the 32-bit MMU implementation and which can be skipped if
we opencode the memset in __mmu_init.

>  
>  	return new_table;
>  }
> +#endif
>  
>  static __maybe_unused uint64_t *find_pte(uint64_t addr)
>  {
> @@ -81,7 +95,7 @@ static void split_block(uint64_t *pte, int level)
>  	/* level describes the parent level, we need the child ones */
>  	levelshift = level2shift(level + 1);
>  
> -	new_table = create_table();
> +	new_table = alloc_pte();
>  
>  	for (i = 0; i < MAX_PTE_ENTRIES; i++) {
>  		new_table[i] = old_pte | (i << levelshift);
> @@ -183,7 +197,7 @@ void __mmu_init(bool mmu_on)
>  	if (mmu_on)
>  		mmu_disable();
>  
> -	ttb = create_table();
> +	ttb = alloc_pte();
>  	el = current_el();
>  	set_ttbr_tcr_mair(el, (uint64_t)ttb, calc_tcr(el, BITS_PER_VA),
>  			  MEMORY_ATTRIBUTES);

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