Re: [linux-next:master 10679/10701] arch/x86/mm/pgtable.c:427:2: warning: variable length array 'u_pmds' is used

[Mike Rapoport <rppt@linux.ibm.com>]

On Wed, May 20, 2020 at 04:11:01PM -0700, Andrew Morton wrote:
> On Thu, 21 May 2020 03:56:53 +0800 kbuild test robot <lkp@intel.com> wrote:
> 
> > tree:   https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git master
> > head:   fb57b1fabcb28f358901b2df90abd2b48abc1ca8
> > commit: 0e19fc1c40bd7516d5a30a459db4f49d48910847 [10679/10701] mm: consolidate pgd_index() and pgd_offset{_k}() definitions
> > config: i386-randconfig-a005-20200520 (attached as .config)
> > compiler: gcc-4.9 (Ubuntu 4.9.3-13ubuntu2) 4.9.3
> > reproduce:
> >         git checkout 0e19fc1c40bd7516d5a30a459db4f49d48910847
> >         # save the attached .config to linux build tree
> >         make ARCH=i386 
> > 
> > If you fix the issue, kindly add following tag as appropriate
> > Reported-by: kbuild test robot <lkp@intel.com>
> > 
> > All warnings (new ones prefixed by >>, old ones prefixed by <<):
> > 
> > arch/x86/mm/pgtable.c: In function 'pgd_alloc':
> > >> arch/x86/mm/pgtable.c:427:2: warning: variable length array 'u_pmds' is used [-Wvla]
> > pmd_t *u_pmds[MAX_PREALLOCATED_USER_PMDS];
> > ^
> > >> arch/x86/mm/pgtable.c:428:2: warning: variable length array 'pmds' is used [-Wvla]
> > pmd_t *pmds[MAX_PREALLOCATED_PMDS];
> > ^
> 
> Thanks.  This works for me - perhaps Mike can come up with something smarter.

Not really :)
Thanks for the fix!

Acked-by: Mike Rapoport <rppt@linux.ibm.com>

> --- a/include/linux/pgtable.h~mm-consolidate-pgd_index-and-pgd_offset_k-definitions-fix
> +++ a/include/linux/pgtable.h
> @@ -62,11 +62,8 @@ static inline unsigned long pud_index(un
>  #endif
>  
>  #ifndef pgd_index
> -static inline unsigned long pgd_index(unsigned long address)
> -{
> -	return ((address >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1));
> -}
> -#define pgd_index pgd_index
> +/* Must be a compile-time constant, so implement it as a macro */
> +#define pgd_index(a)  (((a) >> PGDIR_SHIFT) & (PTRS_PER_PGD - 1))
>  #endif
>  
>  #ifndef pte_offset_kernel
> _
> 

-- 
Sincerely yours,
Mike.