[PATCH] arm64: kernel: Replace manual computation with macro

[Catalin Marinas]

On Fri, May 17, 2024 at 06:54:21PM +0530, Dev Jain wrote:
> diff --git a/arch/arm64/kernel/pi/map_range.c b/arch/arm64/kernel/pi/map_range.c
> index 5410b2cac590..4b145be7f846 100644
> --- a/arch/arm64/kernel/pi/map_range.c
> +++ b/arch/arm64/kernel/pi/map_range.c
> @@ -31,14 +31,14 @@ void __init map_range(u64 *pte, u64 start, u64 end, u64 pa, pgprot_t prot,
>  {
>  	u64 cmask = (level == 3) ? CONT_PTE_SIZE - 1 : U64_MAX;
>  	u64 protval = pgprot_val(prot) & ~PTE_TYPE_MASK;
> -	int lshift = (3 - level) * (PAGE_SHIFT - 3);
> -	u64 lmask = (PAGE_SIZE << lshift) - 1;
> +	int lshift = ARM64_HW_PGTABLE_LEVEL_SHIFT(level);
> +	u64 lmask = ((u64)1 << lshift) - 1;

Nitpick: you can use 1UL instead of (u64)1.

>  
>  	start	&= PAGE_MASK;
>  	pa	&= PAGE_MASK;
>  
>  	/* Advance tbl to the entry that covers start */
> -	tbl += (start >> (lshift + PAGE_SHIFT)) % PTRS_PER_PTE;
> +	tbl += (start >> lshift) % PTRS_PER_PTE;

I did the maths as well my own way and the change is correct:

	lshift + PAGE_SHIT == ARM64_HW_PGTABLE_LEVEL_SHIFT(level)

It probably is easier to read this way, so:

Reviewed-by: Catalin Marinas <catalin.marinas at arm.com>