Subject: Re: [PATCH v2 22/25] powerpc32: move xxxxx_dcache_range() functions inline

From: Scott Wood <[email-masked]>
Date: Thu, 8 Oct 2015 14:12:48 -0500

On Wed, 2015-10-07 at 14:49 +0200, Christophe Leroy wrote:
> Le 29/09/2015 02:29, Scott Wood a écrit :
> > On Tue, Sep 22, 2015 at 06:51:13PM +0200, Christophe Leroy wrote:
> > > flush/clean/invalidate _dcache_range() functions are all very
> > > similar and are quite short. They are mainly used in __dma_sync()
> > > perf_event locate them in the top 3 consumming functions during
> > > heavy ethernet activity
> > > 
> > > They are good candidate for inlining, as __dma_sync() does
> > > almost nothing but calling them
> > > 
> > > Signed-off-by: Christophe Leroy <[email-masked]>
> > > ---
> > > New in v2
> > > 
> > >   arch/powerpc/include/asm/cacheflush.h | 55 
> > > +++++++++++++++++++++++++++--
> > >   arch/powerpc/kernel/misc_32.S         | 65 ---------------------------
> > > --------
> > >   arch/powerpc/kernel/ppc_ksyms.c       |  2 ++
> > >   3 files changed, 54 insertions(+), 68 deletions(-)
> > > 
> > > diff --git a/arch/powerpc/include/asm/cacheflush.h 
> > > b/arch/powerpc/include/asm/cacheflush.h
> > > index 6229e6b..6169604 100644
> > > --- a/arch/powerpc/include/asm/cacheflush.h
> > > +++ b/arch/powerpc/include/asm/cacheflush.h
> > > @@ -47,12 +47,61 @@ static inline void 
> > > __flush_dcache_icache_phys(unsigned long physaddr)
> > >   }
> > >   #endif
> > >   
> > > -extern void flush_dcache_range(unsigned long start, unsigned long 
> > > stop);
> > >   #ifdef CONFIG_PPC32
> > > -extern void clean_dcache_range(unsigned long start, unsigned long 
> > > stop);
> > > -extern void invalidate_dcache_range(unsigned long start, unsigned long 
> > > stop);
> > > +/*
> > > + * Write any modified data cache blocks out to memory and invalidate 
> > > them.
> > > + * Does not invalidate the corresponding instruction cache blocks.
> > > + */
> > > +static inline void flush_dcache_range(unsigned long start, unsigned 
> > > long stop)
> > > +{
> > > + void *addr = (void *)(start & ~(L1_CACHE_BYTES - 1));
> > > + unsigned int size = stop - (unsigned long)addr + (L1_CACHE_BYTES - 1);
> > > + unsigned int i;
> > > +
> > > + for (i = 0; i < size >> L1_CACHE_SHIFT; i++, addr += L1_CACHE_BYTES)
> > > +         dcbf(addr);
> > > + if (i)
> > > +         mb();   /* sync */
> > > +}
> > I know this is 32-bit-specific code, but it's still bad practice to use
> > "unsigned int" for addresses or sizes thereof.
> > 
> > 
> Ok, I can fix size, but what about start and stop ? If I change that, it 
> means I also have to fix all caller. Do you expect me to do that ?

start and stop are already unsigned long.

> And it is very unlykely, but what if for some reason someone wants to 
> invalidate the entire user address space which is 3Gbytes size ? A 
> signed size would be negative here.

Why would size be signed?

-Scott