linux-kernel - Re: [PATCH] mm,x86: fix SMP x86 32bit build for native_pud

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Date:   Mon, 27 Feb 2017 14:29:36 -0500
From:   Boris Ostrovsky <boris.ostrovsky@...cle.com>
To:     labbott@...hat.com
Cc:     dave.jiang@...el.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [PATCH] mm,x86: fix SMP x86 32bit build for native_pud_clear()

> On 02/15/2017 12:31 PM, Dave Jiang wrote:
>> The fix introduced by e4decc90 to fix the UP case for 32bit x86, however
>> that broke the SMP case that was working previously. Add ifdef so the dummy
>> function only show up for 32bit UP case only.
>> 
>> Fix: e4decc90 mm,x86: native_pud_clear missing on i386 build
>> 
>> Reported-by: Alexander Kapshuk <alexander.kapshuk@...il.com>
>> Signed-off-by: Dave Jiang <dave.jiang@...el.com>
>> ---
>>  arch/x86/include/asm/pgtable-3level.h |    2 ++
>>  1 file changed, 2 insertions(+)
>> 
>> diff --git a/arch/x86/include/asm/pgtable-3level.h b/arch/x86/include/asm/pgtable-3level.h
>> index 50d35e3..8f50fb3 100644
>> --- a/arch/x86/include/asm/pgtable-3level.h
>> +++ b/arch/x86/include/asm/pgtable-3level.h
>> @@ -121,9 +121,11 @@ static inline void native_pmd_clear(pmd_t *pmd)
>>  	*(tmp + 1) = 0;
>>  }
>>  
>> +#ifndef CONFIG_SMP
>>  static inline void native_pud_clear(pud_t *pudp)
>>  {
>>  }
>> +#endif
>>  
>>  static inline void pud_clear(pud_t *pudp)
>>  {
>> 

> 
> This breaks one of the Fedora configurations as of 
> e5d56efc97f8240d0b5d66c03949382b6d7e5570
> 
> In file included from ./include/linux/mm.h:68:0,
>                  from ./include/linux/highmem.h:7,
>                  from ./include/linux/bio.h:21,
>                  from ./include/linux/writeback.h:205,
>                  from ./include/linux/memcontrol.h:30,
>                  from ./include/linux/swap.h:8,
>                  from ./include/linux/suspend.h:4,
>                  from arch/x86/kernel/asm-offsets.c:12:
> ./arch/x86/include/asm/pgtable.h: In function 'native_local_pudp_get_and_clear':
> ./arch/x86/include/asm/pgtable.h:888:2: error: implicit declaration of function 'native_pud_clear';did you mean 'native_pmd_clear'? [-Werror=implicit-function-declaration]
>   native_pud_clear(pudp);
>   ^~~~~~~~~~~~~~~~
> 
> Kernel configuration attached. I'm probably just going to revert
> this part unless someone sends me a better fix.


This breakage happens when CONFIG_HIGHMEM64G (i.e. CONFIG_X86_PAE) and CONFIG_PARAVIRT.

-boris