Subject: Re: Linux-next-20200302: arm64 build failed

From: Anshuman Khandual <[email-masked]>
Date: Tue, 3 Mar 2020 09:34:45 +0530

On 03/02/2020 11:15 PM, Catalin Marinas wrote:
> On Mon, Mar 02, 2020 at 03:54:43PM +0200, Mike Rapoport wrote:
>> On Mon, Mar 02, 2020 at 10:47:27AM +0000, Will Deacon wrote:
>>> [+Anshuman and Catalin]
>>>
>>> On Mon, Mar 02, 2020 at 01:58:26PM +0530, Naresh Kamboju wrote:
>>>> Linux-Next 20200302 arm64 build failed due to below errors,
>>>> Suspecting patch causing this build break.
>>>>
>>>> 87d900aef3e2  arm/arm64: add support for folded p4d page tables
>>>>
>>>> Error log,
>>>> -------------
>>>> arch/arm64/mm/mmu.c: In function 'unmap_hotplug_pud_range':
>>>> include/linux/compiler.h:284:1: error: incompatible type for argument
>>>> 1 of 'p4d_page_paddr'
>>>>  ({         \
>>>>  ^
>>>> arch/arm64/include/asm/memory.h:270:45: note: in definition of macro
>>>> '__phys_to_virt'
>>>>  #define __phys_to_virt(x) ((unsigned long)((x) - physvirt_offset))
>>>>                                              ^
>>>> arch/arm64/include/asm/pgtable.h:629:42: note: in expansion of macro '__va'
>>>>  #define pud_offset(dir, addr)  ((pud_t *)__va(pud_offset_phys((dir), (addr))))
>>>>                                           ^~~~
>>>> include/linux/compiler.h:293:22: note: in expansion of macro '__READ_ONCE'
>>>>  #define READ_ONCE(x) __READ_ONCE(x, 1)
>>>>                       ^~~~~~~~~~~
>>>> arch/arm64/include/asm/pgtable.h:628:52: note: in expansion of macro 'READ_ONCE'
>>>>  #define pud_offset_phys(dir, addr) (p4d_page_paddr(READ_ONCE(*(dir)))
>>>> + pud_index(addr) * sizeof(pud_t))
>>>>                                                     ^~~~~~~~~
>>>> arch/arm64/include/asm/pgtable.h:629:47: note: in expansion of macro
>>>> 'pud_offset_phys'
>>>>  #define pud_offset(dir, addr)  ((pud_t *)__va(pud_offset_phys((dir), (addr))))
>>>>                                                ^~~~~~~~~~~~~~~
>>>> arch/arm64/mm/mmu.c:827:10: note: in expansion of macro 'pud_offset'
>>>>    pudp = pud_offset(pgdp, addr);
>>>>           ^~~~~~~~~~
>>>
>>> Looks like we need an implementation of unmap_hotplug_p4d_range() to
>>> walk the dummy p4d level. Unfortunately, we don't have the folded p4d
>>> patches in the arm64 tree so we'll either need a common branch or the
>>> hotplug patches will need to be dropped for the moment.
>>
>> unmap_hotplug_p4d_range() is easy :)
>>
>> From c7a5d08ff51ca2057b6b0289c4423bdfd7643518 Mon Sep 17 00:00:00 2001
>> From: Mike Rapoport <[email-masked]>
>> Date: Mon, 2 Mar 2020 15:53:17 +0200
>> Subject: [PATCH] arm64/mm: implement unmap_hotplug_p4d_range
>>
>> Signed-off-by: Mike Rapoport <[email-masked]>
>> ---
>>  arch/arm64/mm/mmu.c | 20 +++++++++++++++++++-
>>  1 file changed, 19 insertions(+), 1 deletion(-)
>>
>> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
>> index 05ec8e5f1436..c76b11577558 100644
>> --- a/arch/arm64/mm/mmu.c
>> +++ b/arch/arm64/mm/mmu.c
>> @@ -840,6 +840,24 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
>>  	} while (addr = next, addr < end);
>>  }
>>  
>> +static void unmap_hotplug_p4d_range(pgd_t *pgd, unsigned long addr,
>> +				unsigned long end, bool free_mapped)
>> +{
>> +	unsigned long next;
>> +	pgd_t *p4dp, p4d;
>> +
>> +	do {
>> +		next = p4d_addr_end(addr, end);
>> +		p4dp = p4d_offset(pgd, addr);
>> +		p4d = READ_ONCE(*p4dp);
>> +		if (p4d_none(p4d))
>> +			continue;
>> +
>> +		WARN_ON(!p4d_present(p4d));
>> +		unmap_hotplug_pud_range(p4dp, addr, next, free_mapped);
>> +	} while (addr = next, addr < end);
>> +}
>> +
>>  static void unmap_hotplug_range(unsigned long addr, unsigned long end,
>>  				bool free_mapped)
>>  {
>> @@ -854,7 +872,7 @@ static void unmap_hotplug_range(unsigned long addr, unsigned long end,
>>  			continue;
>>  
>>  		WARN_ON(!pgd_present(pgd));
>> -		unmap_hotplug_pud_range(pgdp, addr, next, free_mapped);
>> +		unmap_hotplug_p4d_range(pgdp, addr, next, free_mapped);
>>  	} while (addr = next, addr < end);
>>  }
> 
> Thanks Mike. With the additional diff below, I can get it to build with
> and without the p4d clean-up patches in -next. If Anshuman confirms that
> they work, I can add them on top of the arm64 for-next/memory-hotremove
> branch.

These two patches applied on next-20200302 works fine for hot-remove. As the
second patch also fixes the first one, IMHO both should be folded into a
single one instead. Just wondering if this combined patch which enables P4D
page table should be posted on the list or do I need to respin original hot
remove patches again.

- Anshuman

> 
> ----------8<------------------------
> diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c
> index 56bd9227937f..2faf11860097 100644
> --- a/arch/arm64/mm/mmu.c
> +++ b/arch/arm64/mm/mmu.c
> @@ -816,7 +816,7 @@ static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr,
>  	} while (addr = next, addr < end);
>  }
>  
> -static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
> +static void unmap_hotplug_pud_range(p4d_t *p4dp, unsigned long addr,
>  				    unsigned long end, bool free_mapped)
>  {
>  	unsigned long next;
> @@ -824,7 +824,7 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
>  
>  	do {
>  		next = pud_addr_end(addr, end);
> -		pudp = pud_offset(pgdp, addr);
> +		pudp = pud_offset(p4dp, addr);
>  		pud = READ_ONCE(*pudp);
>  		if (pud_none(pud))
>  			continue;
> @@ -848,15 +848,15 @@ static void unmap_hotplug_pud_range(pgd_t *pgdp, unsigned long addr,
>  	} while (addr = next, addr < end);
>  }
>  
> -static void unmap_hotplug_p4d_range(pgd_t *pgd, unsigned long addr,
> -				unsigned long end, bool free_mapped)
> +static void unmap_hotplug_p4d_range(pgd_t *pgdp, unsigned long addr,
> +				    unsigned long end, bool free_mapped)
>  {
>  	unsigned long next;
> -	pgd_t *p4dp, p4d;
> +	p4d_t *p4dp, p4d;
>  
>  	do {
>  		next = p4d_addr_end(addr, end);
> -		p4dp = p4d_offset(pgd, addr);
> +		p4dp = p4d_offset(pgdp, addr);
>  		p4d = READ_ONCE(*p4dp);
>  		if (p4d_none(p4d))
>  			continue;
> @@ -961,7 +961,7 @@ static void free_empty_pmd_table(pud_t *pudp, unsigned long addr,
>  	free_hotplug_pgtable_page(virt_to_page(pmdp));
>  }
>  
> -static void free_empty_pud_table(pgd_t *pgdp, unsigned long addr,
> +static void free_empty_pud_table(p4d_t *p4dp, unsigned long addr,
>  				 unsigned long end, unsigned long floor,
>  				 unsigned long ceiling)
>  {
> @@ -970,7 +970,7 @@ static void free_empty_pud_table(pgd_t *pgdp, unsigned long addr,
>  
>  	do {
>  		next = pud_addr_end(addr, end);
> -		pudp = pud_offset(pgdp, addr);
> +		pudp = pud_offset(p4dp, addr);
>  		pud = READ_ONCE(*pudp);
>  		if (pud_none(pud))
>  			continue;
> @@ -990,17 +990,36 @@ static void free_empty_pud_table(pgd_t *pgdp, unsigned long addr,
>  	 * entries are empty. Overlap with other regions have been
>  	 * handled by the floor/ceiling check.
>  	 */
> -	pudp = pud_offset(pgdp, 0UL);
> +	pudp = pud_offset(p4dp, 0UL);
>  	for (i = 0; i < PTRS_PER_PUD; i++) {
>  		if (!pud_none(READ_ONCE(pudp[i])))
>  			return;
>  	}
>  
> -	pgd_clear(pgdp);
> +	p4d_clear(p4dp);
>  	__flush_tlb_kernel_pgtable(start);
>  	free_hotplug_pgtable_page(virt_to_page(pudp));
>  }
>  
> +static void free_empty_p4d_table(pgd_t *pgdp, unsigned long addr,
> +				 unsigned long end, unsigned long floor,
> +				 unsigned long ceiling)
> +{
> +	p4d_t *p4dp, p4d;
> +	unsigned long next;
> +
> +	do {
> +		next = p4d_addr_end(addr, end);
> +		p4dp = p4d_offset(pgdp, addr);
> +		p4d = READ_ONCE(*p4dp);
> +		if (p4d_none(p4d))
> +			continue;
> +
> +		WARN_ON(!p4d_present(p4d));
> +		free_empty_pud_table(p4dp, addr, next, floor, ceiling);
> +	} while (addr = next, addr < end);
> +}
> +
>  static void free_empty_tables(unsigned long addr, unsigned long end,
>  			      unsigned long floor, unsigned long ceiling)
>  {
> @@ -1015,7 +1034,7 @@ static void free_empty_tables(unsigned long addr, unsigned long end,
>  			continue;
>  
>  		WARN_ON(!pgd_present(pgd));
> -		free_empty_pud_table(pgdp, addr, next, floor, ceiling);
> +		free_empty_p4d_table(pgdp, addr, next, floor, ceiling);
>  	} while (addr = next, addr < end);
>  }
>  #endif
>