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

From: Anshuman Khandual <[email-masked]>
Date: Mon, 2 Mar 2020 19:18:16 +0530

On 03/02/2020 04:17 PM, 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.

If we decide to get a common branch, will try to get this sorted with
an unmap_hotplug_p4d_range() implementation as you have suggested.

> Will