Re: [PATCH v1] RISC-V: Add braces around an empty if statement bodies

[Palmer Dabbelt]

On Tue, 19 Apr 2022 13:38:42 PDT (-0700), rdunlap@xxxxxxxxxxxxx wrote:
> Hi,
>
> On 4/19/22 12:48, Palmer Dabbelt wrote:
> > From: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> >
> > This triggers -Wempty-body, which will cause the next statement (eventually
> > create_pmd_mapping) to be dropped.  Both of these were introduced by the same
> > commit.  This is safe for the reporting config (which is 32-bit), but IIUC
> > could result in breakages for 64-bit configs without 4/5 level paging like the
> > XIP configs.
> >
> > Reported-by: kernel test robot <lkp@xxxxxxxxx>
> > Fixes: 677b9eb8810e ("riscv: mm: Prepare pt_ops helper functions for sv57")
> > Signed-off-by: Palmer Dabbelt <palmer@xxxxxxxxxxxx>
> > ---
> > Might be better to define these to functions that are empty, but that's
> > slightly different than just fixing the commit/warning in question.
>
> Yes, we usually fix this type of problem by changing these to have empty bodies:
>
> #else
> ...
> #define create_pud_mapping(__pmdp, __va, __pa, __sz, __prot)
> #define create_pmd_mapping(__pmdp, __va, __pa, __sz, __prot)
> #endif /* __PAGETABLE_PMD_FOLDED */
>
> etc.

Ya, that's the right way to do it -- not sure why I was being lazy here.  
Turns out there was a bunch of other XIP breakage, I sent a v2 that's a 
whole series.

Thanks!

> > ---
> >  arch/riscv/mm/init.c | 6 ++++--
> >  1 file changed, 4 insertions(+), 2 deletions(-)
> >
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index 9535bea8688c..637916857c4d 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -798,13 +798,15 @@ static void __init create_fdt_early_page_table(pgd_t *pgdir, uintptr_t dtb_pa)
> >  			   PGDIR_SIZE,
> >  			   IS_ENABLED(CONFIG_64BIT) ? PAGE_TABLE : PAGE_KERNEL);
> >
> > -	if (pgtable_l5_enabled)
> > +	if (pgtable_l5_enabled) {
> >  		create_p4d_mapping(early_dtb_p4d, DTB_EARLY_BASE_VA,
> >  				   (uintptr_t)early_dtb_pud, P4D_SIZE, PAGE_TABLE);
> > +	}
> >
> > -	if (pgtable_l4_enabled)
> > +	if (pgtable_l4_enabled) {
> >  		create_pud_mapping(early_dtb_pud, DTB_EARLY_BASE_VA,
> >  				   (uintptr_t)early_dtb_pmd, PUD_SIZE, PAGE_TABLE);
> > +	}
> >
> >  	if (IS_ENABLED(CONFIG_64BIT)) {
> >  		create_pmd_mapping(early_dtb_pmd, DTB_EARLY_BASE_VA,