Re: [RFCv3][PATCH 1/3] create slow_virt_to_phys()

[H. Peter Anvin]

On 01/09/2013 10:59 AM, Dave Hansen wrote:
> +	switch (level) {
> +	case PG_LEVEL_4K:
> +		psize = PAGE_SIZE;
> +		pmask = PAGE_MASK;
> +		break;
> +	case PG_LEVEL_2M:
> +		psize = PMD_PAGE_SIZE;
> +		pmask = PMD_PAGE_MASK;
> +		break;
> +#ifdef CONFIG_X86_64
> +	case PG_LEVEL_1G:
> +		psize = PUD_PAGE_SIZE;
> +		pmask = PUD_PAGE_MASK;
> +		break;
> +#endif
> +	default:
> +		BUG();
> +	}

I object to this switch statement.  If we are going to create new 
primitives, let's create a primitive that embody this and put it in 
pgtypes_types.h, especially since it is simply an algorithmic operation:

static inline unsigned long page_level_size(int level)
{
	return (PAGE_SIZE/PGDIR_SIZE) << (PGDIR_SHIFT*level);
}
static inline unsigned long page_level_shift(int level)
{
	return (PAGE_SHIFT-PGDIR_SHIFT) + (PGDIR_SHIFT*level);
}

--
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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