linux-kernel - Re: [RFC V2 2/3] arm64/mm: Define arch_get_mappable

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Message-ID: <85975346-d5ae-d971-e50f-9c0b77649910@arm.com>
Date:   Wed, 2 Dec 2020 17:47:01 +0530
From:   Anshuman Khandual <anshuman.khandual@....com>
To:     David Hildenbrand <david@...hat.com>, linux-mm@...ck.org,
        akpm@...ux-foundation.org
Cc:     linux-arm-kernel@...ts.infradead.org, linux-s390@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>,
        Ard Biesheuvel <ardb@...nel.org>,
        Mark Rutland <mark.rutland@....com>
Subject: Re: [RFC V2 2/3] arm64/mm: Define arch_get_mappable_range()



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@....com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Ard Biesheuvel <ardb@...nel.org>
>> Cc: Mark Rutland <mark.rutland@....com>
>> Cc: David Hildenbrand <david@...hat.com>
>> Cc: linux-arm-kernel@...ts.infradead.org
>> Cc: linux-kernel@...r.kernel.org
>> Signed-off-by: Anshuman Khandual <anshuman.khandual@....com>
>> ---
>>  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!
>