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

From: Anshuman Khandual <[email-masked]>
Date: Wed, 4 Mar 2020 10:02:38 +0530

On 03/04/2020 07:56 AM, Anshuman Khandual wrote:
> 
> 
> On 03/03/2020 09:58 PM, Catalin Marinas wrote:
>> On Tue, Mar 03, 2020 at 09:34:45AM +0530, Anshuman Khandual wrote:
>>> 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.
>>
>> Do they also work on top of the vanilla kernel + your hotremove patches
>> (i.e. not on top of -next)?
> 
> Yes, they do work on current vanilla kernel (8b614cb8f1dcac8ca77cf4dd85f46)
> and v13 hotremove series.
> 
>>
>>> 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.
>>
>> If your unmap patches plus the fixes from Mike and me work fine on top
>> of 5.6-rc3 (as well as when combined with linux-next), I'd prefer you
> Yes, they do work on both.
> 
>> respin your patches to include the p4d support from start. Otherwise, we
> 
> Okay. I will be sending V14 on v5.6-rc3 (OR v.5.6-rc4 is preferred ?) with
> p4d support. I will add yours and Mike's Signed-off-by as well.

Posted V14 (https://patchwork.kernel.org/project/linux-mm/list/?series=250939)
for the arm64 hot remove series on v5.6-rc3, though it also applies and works
on 5.6-rc4 as well.

> 
>> create a single patch that Andrew can merge on top of the -mm tree.
>>