Re: [PATCH V2 2/2] arm64/mm: Reorganize pfn_valid()

[David Hildenbrand <david@redhat.com>]

On 02.02.21 05:11, Anshuman Khandual wrote:
> There are multiple instances of pfn_to_section_nr() and __pfn_to_section()
> when CONFIG_SPARSEMEM is enabled. This can be optimized if memory section
> is fetched earlier. This replaces the open coded PFN and ADDR conversion
> with PFN_PHYS() and PHYS_PFN() helpers. While there, also add a comment.
> This does not cause any functional change.
> 
> Cc: Catalin Marinas <catalin.marinas@arm.com>
> Cc: Will Deacon <will@kernel.org>
> Cc: Ard Biesheuvel <ardb@kernel.org>
> Cc: linux-arm-kernel@lists.infradead.org
> Cc: linux-kernel@vger.kernel.org
> Signed-off-by: Anshuman Khandual <anshuman.khandual@arm.com>
> ---
>   arch/arm64/mm/init.c | 20 +++++++++++++++-----
>   1 file changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/arm64/mm/init.c b/arch/arm64/mm/init.c
> index 1141075e4d53..5d8fd5360a68 100644
> --- a/arch/arm64/mm/init.c
> +++ b/arch/arm64/mm/init.c
> @@ -219,16 +219,25 @@ static void __init zone_sizes_init(unsigned long min, unsigned long max)
>   
>   int pfn_valid(unsigned long pfn)
>   {
> -	phys_addr_t addr = pfn << PAGE_SHIFT;
> +	phys_addr_t addr = PFN_PHYS(pfn);
>   
> -	if ((addr >> PAGE_SHIFT) != pfn)
> +	/*
> +	 * Ensure the upper PAGE_SHIFT bits are clear in the
> +	 * pfn. Else it might lead to false positives when
> +	 * some of the upper bits are set, but the lower bits
> +	 * match a valid pfn.
> +	 */
> +	if (PHYS_PFN(addr) != pfn)
>   		return 0;
>   
>   #ifdef CONFIG_SPARSEMEM
> +{
> +	struct mem_section *ms = __pfn_to_section(pfn);
> +
>   	if (pfn_to_section_nr(pfn) >= NR_MEM_SECTIONS)
>   		return 0;
>   
> -	if (!valid_section(__pfn_to_section(pfn)))
> +	if (!valid_section(ms))
>   		return 0;
>   
>   	/*
> @@ -240,8 +249,9 @@ int pfn_valid(unsigned long pfn)
>   	 * memory sections covering all of hotplug memory including
>   	 * both normal and ZONE_DEVICE based.
>   	 */
> -	if (!early_section(__pfn_to_section(pfn)))
> -		return pfn_section_valid(__pfn_to_section(pfn), pfn);
> +	if (!early_section(ms))
> +		return pfn_section_valid(ms, pfn);
> +}
>   #endif
>   	return memblock_is_map_memory(addr);
>   }
> 

Reviewed-by: David Hildenbrand <david@redhat.com>

-- 
Thanks,

David / dhildenb