Re: Linux-next-20200302: arm64 build failed

[Will Deacon]

[+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.

Will