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Subject: Re: [PATCH 16/18] ARC: mm: support 4 levels of page tables
To:     Mike Rapoport <rppt@kernel.org>
Cc:     linux-snps-arc@lists.infradead.org, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org, Anshuman Khandual <anshuman.khandual@arm.com>
References: <20210811004258.138075-1-vgupta@kernel.org>
 <20210811004258.138075-17-vgupta@kernel.org> <YRPCaxDC5f8N9jHW@kernel.org>
From:   Vineet Gupta <vgupta@kernel.org>
Message-ID: <cfe75b58-0783-5997-c05f-3c7db88508f8@kernel.org>
Date:   Wed, 11 Aug 2021 15:17:01 -0700
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On 8/11/21 5:28 AM, Mike Rapoport wrote:
> On Tue, Aug 10, 2021 at 05:42:56PM -0700, Vineet Gupta wrote:
>> Signed-off-by: Vineet Gupta<vgupta@kernel.org>
>> ---
>>   arch/arc/include/asm/page.h           | 11 +++++++
>>   arch/arc/include/asm/pgalloc.h        | 22 +++++++++++++
>>   arch/arc/include/asm/pgtable-levels.h | 45 ++++++++++++++++++++++++---
>>   arch/arc/mm/fault.c                   |  2 ++
>>   arch/arc/mm/tlbex.S                   |  9 ++++++
>>   5 files changed, 84 insertions(+), 5 deletions(-)
>>
>> diff --git a/arch/arc/include/asm/page.h b/arch/arc/include/asm/page.h
>> index df3cc154ae4a..883856f12afe 100644
>> --- a/arch/arc/include/asm/page.h
>> +++ b/arch/arc/include/asm/page.h
>> @@ -41,6 +41,17 @@ typedef struct {
>>   #define pgd_val(x)	((x).pgd)
>>   #define __pgd(x)	((pgd_t) { (x) })
>>   
>> +#if CONFIG_PGTABLE_LEVELS > 3
>> +
>> +typedef struct {
>> +	unsigned long pud;
>> +} pud_t;
>> +
>> +#define pud_val(x)      	((x).pud)
>> +#define __pud(x)        	((pud_t) { (x) })
>> +
>> +#endif
>> +
>>   #if CONFIG_PGTABLE_LEVELS > 2
>>   
>>   typedef struct {
>> diff --git a/arch/arc/include/asm/pgalloc.h b/arch/arc/include/asm/pgalloc.h
>> index 01c2d84418ed..e99c724d9235 100644
>> --- a/arch/arc/include/asm/pgalloc.h
>> +++ b/arch/arc/include/asm/pgalloc.h
>> @@ -86,6 +86,28 @@ static inline void pgd_free(struct mm_struct *mm, pgd_t *pgd)
>>   }
>>   
>>   
>> +#if CONFIG_PGTABLE_LEVELS > 3
>> +
>> +static inline void p4d_populate(struct mm_struct *mm, p4d_t *p4dp, pud_t *pudp)
>> +{
>> +	set_p4d(p4dp, __p4d((unsigned long)pudp));
>> +}
>> +
>> +static inline pud_t *pud_alloc_one(struct mm_struct *mm, unsigned long addr)
>> +{
>> +	return (pud_t *)__get_free_page(
>> +		GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_ZERO);
>> +}
>> +
>> +static inline void pud_free(struct mm_struct *mm, pud_t *pudp)
>> +{
>> +	free_page((unsigned long)pudp);
>> +}
>> +
>> +#define __pud_free_tlb(tlb, pmd, addr)  pud_free((tlb)->mm, pmd)
>> +
>> +#endif
>> +
>>   #if CONFIG_PGTABLE_LEVELS > 2
>>   
>>   static inline void pud_populate(struct mm_struct *mm, pud_t *pudp, pmd_t *pmdp)
>> diff --git a/arch/arc/include/asm/pgtable-levels.h b/arch/arc/include/asm/pgtable-levels.h
>> index 1c2f022d4ad0..2da3c4e52a91 100644
>> --- a/arch/arc/include/asm/pgtable-levels.h
>> +++ b/arch/arc/include/asm/pgtable-levels.h
>> @@ -44,8 +44,13 @@
>>   /*
>>    * A default 3 level paging testing setup in software walked MMU
>>    *   MMUv4 (8K page): <4> : <7> : <8> : <13>
>> + * A default 4 level paging testing setup in software walked MMU
>> + *   MMUv4 (8K page): <4> : <3> : <4> : <8> : <13>
>>    */
>>   #define PGDIR_SHIFT		28
>> +#if CONFIG_PGTABLE_LEVELS > 3
>> +#define PUD_SHIFT		25
>> +#endif
>>   #if CONFIG_PGTABLE_LEVELS > 2
>>   #define PMD_SHIFT		21
>>   #endif
>> @@ -56,17 +61,25 @@
>>   #define PGDIR_MASK		(~(PGDIR_SIZE - 1))
>>   #define PTRS_PER_PGD		BIT(32 - PGDIR_SHIFT)
>>   
>> +#if CONFIG_PGTABLE_LEVELS > 3
>> +#define PUD_SIZE		BIT(PUD_SHIFT)
>> +#define PUD_MASK		(~(PUD_SIZE - 1))
>> +#define PTRS_PER_PUD		BIT(PGDIR_SHIFT - PUD_SHIFT)
> Maybe move these into the previous #if CONFIG_PGTABLE_LEVELS > 3?

Same reasoning as the prev one. Sure there's a bit more ifdef'ery but I 
think it looks more organized to me. But if you really feel strongly I 
can move the code around.

-Vineet