Re: [RFC V2 2/3] arm64/mm: Define arch_get_mappable_range()

From: Anshuman Khandual
Date: Wed Dec 02 2020 - 07:17:57 EST




On 12/2/20 2:56 PM, David Hildenbrand wrote:
> On 30.11.20 04:29, Anshuman Khandual wrote:
>> This overrides arch_get_mappable_range() on arm64 platform which will be
>> used with recently added generic framework. It drops inside_linear_region()
>> and subsequent check in arch_add_memory() which are no longer required.
>>
>> Cc: Catalin Marinas <catalin.marinas@xxxxxxx>
>> Cc: Will Deacon <will@xxxxxxxxxx>
>> Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
>> Cc: Mark Rutland <mark.rutland@xxxxxxx>
>> Cc: David Hildenbrand <david@xxxxxxxxxx>
>> Cc: linux-arm-kernel@xxxxxxxxxxxxxxxxxxx
>> Cc: linux-kernel@xxxxxxxxxxxxxxx
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@xxxxxxx>
>> ---
>> arch/arm64/mm/mmu.c | 14 ++++++--------
>> 1 file changed, 6 insertions(+), 8 deletions(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index ca692a815731..49ec8f2838f2 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -1444,16 +1444,19 @@ static void __remove_pgd_mapping(pgd_t *pgdir, unsigned long start, u64 size)
>> free_empty_tables(start, end, PAGE_OFFSET, PAGE_END);
>> }
>>
>> -static bool inside_linear_region(u64 start, u64 size)
>> +struct range arch_get_mappable_range(void)
>> {
>> + struct range memhp_range;
>> +
>> /*
>> * Linear mapping region is the range [PAGE_OFFSET..(PAGE_END - 1)]
>> * accommodating both its ends but excluding PAGE_END. Max physical
>> * range which can be mapped inside this linear mapping range, must
>> * also be derived from its end points.
>> */
>> - return start >= __pa(_PAGE_OFFSET(vabits_actual)) &&
>> - (start + size - 1) <= __pa(PAGE_END - 1);
>> + memhp_range.start = __pa(_PAGE_OFFSET(vabits_actual));
>> + memhp_range.end = __pa(PAGE_END - 1);
>> + return memhp_range;
>> }
>>
>> int arch_add_memory(int nid, u64 start, u64 size,
>> @@ -1461,11 +1464,6 @@ int arch_add_memory(int nid, u64 start, u64 size,
>> {
>> int ret, flags = 0;
>>
>> - if (!inside_linear_region(start, size)) {
>> - pr_err("[%llx %llx] is outside linear mapping region\n", start, start + size);
>> - return -EINVAL;
>> - }
> As discussed, I think something like a VM_BUG_ON() here might makes
> sense, indicating that we require the caller to validate upfront. Same
> applies to the s390x variant.

Sure, will do.

>
> Thanks!
>