Re: [bug report] powerpc/mm/radix: Add tlbflush routines

On 01/31/2018 09:31 PM, Christophe LEROY wrote:

Le 31/01/2018 à 16:45, Dan Carpenter a écrit :

quoted

Hello Aneesh Kumar K.V,

The patch 1a472c9dba6b: "powerpc/mm/radix: Add tlbflush routines"
from Apr 29, 2016, leads to the following static checker warning:

    arch/powerpc/mm/tlb_nohash.c:218 __local_flush_tlb_page()
    warn: always true condition '(pid != ~0) => (0-u32max != u64max)'

arch/powerpc/mm/tlb_nohash.c
    211  void __local_flush_tlb_page(struct mm_struct *mm, unsigned 
long vmaddr,
    212                              int tsize, int ind)
    213  {
    214          unsigned int pid;
    215
    216          preempt_disable();
    217          pid = mm ? mm->context.id : 0;
    218          if (pid != MMU_NO_CONTEXT)
                     ^^^^^^^^^^^^^^^^^^^^^
    219                  _tlbil_va(vmaddr, pid, tsize, ind);
    220          preempt_enable();
    221  }

I don't know very much about PowerPC.  The static checker is guessing
which headers to pull in instead of relying on the build system so there
are a lot of false positives.  It's apparently using the
arch/powerpc/include/asm/book3s/64/tlbflush.h header which does:

#define MMU_NO_CONTEXT ~0UL

so it's UINT_MAX vs U64_MAX which is making the checker complain.

As far as I can see from arch/powerpc/include/asm/mmu-hash64.h, 
mm->context.id is an unsigned long, so pid should also be an unsigned 
long, not an unsigned int ?

Christophe

yes.

We did similar fixup for book3s radix
in 9690c15742688e9cb5ee4aa0b08e458551ceea13 (powerpc/mm/radix: Fix 
always false comparison against MMU_NO_CONTEXT
)

-aneesh