linux-kernel - Re: [PATCH] parisc: fix map_pages() to actually populate upper directory

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Message-ID: <56969e89-2f86-a50d-1e6f-7360527da54b@gmx.de>
Date:   Sat, 11 Jan 2020 16:53:19 +0100
From:   Helge Deller <deller@....de>
To:     Mike Rapoport <rppt@...ux.ibm.com>
Cc:     Mike Rapoport <rppt@...nel.org>,
        "James E.J. Bottomley" <James.Bottomley@...senpartnership.com>,
        linux-parisc@...r.kernel.org, linux-kernel@...r.kernel.org,
        Meelis Roos <mroos@...ux.ee>, Jeroen Roovers <jer@...too.org>,
        Mikulas Patocka <mpatocka@...hat.com>
Subject: Re: [PATCH] parisc: fix map_pages() to actually populate upper
 directory

On 09.01.20 09:45, Mike Rapoport wrote:
> Hi,
>
> On Thu, Jan 09, 2020 at 07:50:55AM +0100, Helge Deller wrote:
>>> The commit d96885e277b5 ("parisc: use pgtable-nopXd instead of
>>> 4level-fixup") converted PA-RISC to use folded page tables, but it missed
>>> the conversion of pgd_populate() to pud_populate() in maps_pages()
>>> function. This caused the upper page table directory to remain empty and
>>> the system would crash as a result.
>>>
>>> Using pud_populate() that actually populates the page table instead of
>>> dummy pgd_populate() fixes the issue.
>>> ...
>>> diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
>>> index ddca8287d43b..354cf060b67f 100644
>>> --- a/arch/parisc/mm/init.c
>>> +++ b/arch/parisc/mm/init.c
>>> @@ -401,7 +401,7 @@ static void __init map_pages(unsigned long start_vaddr,
>>>  			pmd = (pmd_t *) __pa(pmd);
>>>  		}
>>>
>>> -		pgd_populate(NULL, pg_dir, __va(pmd));
>>> +		pud_populate(NULL, (pud_t *)pg_dir, __va(pmd));
>>>  #endif
>>
>> Wouldn't the untested patch below be more clean?
>>
>> Helge
>>
>> diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
>> index ddca8287d43b..73de58f31f5f 100644
>> --- a/arch/parisc/mm/init.c
>> +++ b/arch/parisc/mm/init.c
>> @@ -387,6 +387,8 @@ static void __init map_pages(unsigned long start_vaddr,
>>  #if PTRS_PER_PMD == 1
>>  		pmd = (pmd_t *)__pa(pg_dir);
>>  #else
>> +		p4d_t *p4d;
>> +		pud_t *pud;
>>  		pmd = (pmd_t *)pgd_address(*pg_dir);
>>
>>  		/*
>> @@ -401,7 +403,9 @@ static void __init map_pages(unsigned long start_vaddr,
>>  			pmd = (pmd_t *) __pa(pmd);
>>  		}
>>
>> -		pgd_populate(NULL, pg_dir, __va(pmd));
>> +		p4d = p4d_offset(pg_dir, vaddr);
>> +		pud = pud_offset(p4d, vaddr);
>> +		pud_populate(NULL, pud, __va(pmd));
>>  #endif
>>  		pg_dir++;
>
> I've tried to keep the changes to minimum :)
> Otherwise I'd go with something even more surgical:


Ok, then let's use the small fix for v5.5, and the bigger one for v5.6.
I'll push the small fixup to Linux through the parisc tree shortly.

Would you mind resending the full cleanup patch for v5.6 later again ?

Thanks!!
Helge

>
> diff --git a/arch/parisc/mm/init.c b/arch/parisc/mm/init.c
> index 354cf060b67f..94baa4382c29 100644
> --- a/arch/parisc/mm/init.c
> +++ b/arch/parisc/mm/init.c
> @@ -351,7 +351,6 @@ static void __init map_pages(unsigned long start_vaddr,
>  			     unsigned long start_paddr, unsigned long size,
>  			     pgprot_t pgprot, int force)
>  {
> -	pgd_t *pg_dir;
>  	pmd_t *pmd;
>  	pte_t *pg_table;
>  	unsigned long end_paddr;
> @@ -372,8 +371,6 @@ static void __init map_pages(unsigned long start_vaddr,
>
>  	end_paddr = start_paddr + size;
>
> -	pg_dir = pgd_offset_k(start_vaddr);
> -
>  #if PTRS_PER_PMD == 1
>  	start_pmd = 0;
>  #else
> @@ -384,50 +381,30 @@ static void __init map_pages(unsigned long start_vaddr,
>  	address = start_paddr;
>  	vaddr = start_vaddr;
>  	while (address < end_paddr) {
> -#if PTRS_PER_PMD == 1
> -		pmd = (pmd_t *)__pa(pg_dir);
> -#else
> -		pmd = (pmd_t *)pgd_address(*pg_dir);
> +		pgd_t *pgd = pgd_offset_k(vaddr);
> +		p4d_t *p4d = p4d_offset(pgd, vaddr);
> +		pud_t *pud = pud_offset(p4d, vaddr);
>
> -		/*
> -		 * pmd is physical at this point
> -		 */
> -
> -		if (!pmd) {
> +#if CONFIG_PGTABLE_LEVELS == 3
> +		if (pud_none(*pud)) {
>  			pmd = memblock_alloc(PAGE_SIZE << PMD_ORDER,
>  					     PAGE_SIZE << PMD_ORDER);
>  			if (!pmd)
>  				panic("pmd allocation failed.\n");
> -			pmd = (pmd_t *) __pa(pmd);
> +			pud_populate(NULL, pud, pmd);
>  		}
> -
> -		pud_populate(NULL, (pud_t *)pg_dir, __va(pmd));
>  #endif
> -		pg_dir++;
>
> -		/* now change pmd to kernel virtual addresses */
> -
> -		pmd = (pmd_t *)__va(pmd) + start_pmd;
> +		pmd = pmd_offset(pud, vaddr);
>  		for (tmp1 = start_pmd; tmp1 < PTRS_PER_PMD; tmp1++, pmd++) {
> -
> -			/*
> -			 * pg_table is physical at this point
> -			 */
> -
> -			pg_table = (pte_t *)pmd_address(*pmd);
> -			if (!pg_table) {
> -				pg_table = memblock_alloc(PAGE_SIZE,
> -							  PAGE_SIZE);
> +			if (pmd_none(*pmd)) {
> +				pg_table = memblock_alloc(PAGE_SIZE, PAGE_SIZE);
>  				if (!pg_table)
>  					panic("page table allocation failed\n");
> -				pg_table = (pte_t *) __pa(pg_table);
> +				pmd_populate_kernel(NULL, pmd, pg_table);
>  			}
>
> -			pmd_populate_kernel(NULL, pmd, __va(pg_table));
> -
> -			/* now change pg_table to kernel virtual addresses */
> -
> -			pg_table = (pte_t *) __va(pg_table) + start_pte;
> +			pg_table = pte_offset_kernel(pmd, vaddr);
>  			for (tmp2 = start_pte; tmp2 < PTRS_PER_PTE; tmp2++, pg_table++) {
>  				pte_t pte;
>  				pgprot_t prot;
>
>