Re: [PATCH linux-5.15.y] RISC-V: Fix up a cherry-pick warning in setup_vm_final()

[Greg KH <gregkh@linuxfoundation.org>]

On Mon, May 01, 2023 at 09:33:25AM +0200, Alexandre Ghiti wrote:
> Hi Palmer,
> 
> On 4/30/23 00:43, Palmer Dabbelt wrote:
> > This triggers a -Wdeclaration-after-statement as the code has changed a
> > bit since upstream.  It might be better to hoist the whole block up, but
> > this is a smaller change so I went with it.
> > 
> > arch/riscv/mm/init.c:755:16: warning: mixing declarations and code is a C99 extension [-Wdeclaration-after-statement]
> >              unsigned long idx = pgd_index(__fix_to_virt(FIX_FDT));
> >                            ^
> >      1 warning generated.
> > 
> > Reported-by: kernel test robot <lkp@intel.com>
> > Link: https://lore.kernel.org/oe-kbuild-all/202304300429.SXZOA5up-lkp@intel.com/
> > Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>
> > ---
> > I haven't even build tested this one, but it looks simple enough that I figured
> > I'd just send it.  Be warned, though: I broke glibc and missed a merged
> > conflict yesterday...
> > ---
> >   arch/riscv/mm/init.c | 3 ++-
> >   1 file changed, 2 insertions(+), 1 deletion(-)
> > 
> > diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> > index e800d7981e99..8d67f43f1865 100644
> > --- a/arch/riscv/mm/init.c
> > +++ b/arch/riscv/mm/init.c
> > @@ -717,6 +717,7 @@ static void __init setup_vm_final(void)
> >   	uintptr_t va, map_size;
> >   	phys_addr_t pa, start, end;
> >   	u64 i;
> > +	unsigned long idx;
> >   	/**
> >   	 * MMU is enabled at this point. But page table setup is not complete yet.
> > @@ -735,7 +736,7 @@ static void __init setup_vm_final(void)
> >   	 * directly in swapper_pg_dir in addition to the pgd entry that points
> >   	 * to fixmap_pte.
> >   	 */
> > -	unsigned long idx = pgd_index(__fix_to_virt(FIX_FDT));
> > +	idx = pgd_index(__fix_to_virt(FIX_FDT));
> >   	set_pgd(&swapper_pg_dir[idx], early_pg_dir[idx]);
> >   #endif
> 
> The above results to in rv64:
> 
> ../arch/riscv/mm/init.c: In function ‘setup_vm_final’:
> ../arch/riscv/mm/init.c:720:16: warning: unused variable ‘idx’
> [-Wunused-variable]
>   720 |  unsigned long idx;
> 
> 
> The following fixes this warning:
> 
> 
> diff --git a/arch/riscv/mm/init.c b/arch/riscv/mm/init.c
> index 8d67f43f1865..e69d82d573f1 100644
> --- a/arch/riscv/mm/init.c
> +++ b/arch/riscv/mm/init.c
> @@ -717,7 +717,7 @@ static void __init setup_vm_final(void)
>         uintptr_t va, map_size;
>         phys_addr_t pa, start, end;
>         u64 i;
> -       unsigned long idx;
> +       unsigned long idx __maybe_unused;
> 
>         /**
>          * MMU is enabled at this point. But page table setup is not
> complete yet.
> 
> 
> Let me know if you want me to send a proper patch as I'm the one to blame
> here.

As the original fix here will not work, a "correct" one might be best to
have :)

thanks,

greg k-h