Subject: Re: [PATCH] powerpc/pseries: Kill all prefetch streams on context switch

From: Michael Neuling <[email-masked]>
Date: Mon, 03 Jun 2013 10:42:19 +1000

Michael Ellerman <[email-masked]> wrote:

> On Thu, May 30, 2013 at 03:34:27PM +1000, Michael Neuling wrote:
> > On context switch, we should have no prefetch streams leak from one
> > userspace process to another.  This frees up prefetch resources for the
> > next process.
> > 
> > Based on patch from Milton Miller.
> > 
> > Signed-off-by: Michael Neuling <[email-masked]>
> > 
> > diff --git a/arch/powerpc/include/asm/ppc_asm.h b/arch/powerpc/include/asm/ppc_asm.h
> > index cea8496..2f1b6c5 100644
> > --- a/arch/powerpc/include/asm/ppc_asm.h
> > +++ b/arch/powerpc/include/asm/ppc_asm.h
> > @@ -523,6 +523,17 @@ END_FTR_SECTION_NESTED(CPU_FTR_HAS_PPR,CPU_FTR_HAS_PPR,946)
> >  #define PPC440EP_ERR42
> >  #endif
> >  
> > +/* The following stops all load and store data streams associated with stream
> > + * ID (ie. streams created explicitly).  The embedded and server mnemonics for
> > + * dcbt are different so we use machine "power4" here explicitly.
> > + */
> > +#define DCBT_STOP_ALL_STREAM_IDS(scratch)	\
> > +.machine push ;					\
> > +.machine "power4" ;				\
> > +       lis     scratch,0x60000000@h;		\
> > +       dcbt    r0,scratch,0b01010;		\
> > +.machine pop
> 
> I don't see why we need the macro, ie. just stick this code in
> entry_64.S directly.

There's a decent chance we'll want to use this again at some point.  We
also most stuck it in the error path of the power7 copy user loop but
after consulting Anton and heavily reviewing the code, we decoded it
shouldn't be needed.

It's in Linus tree now anyway.

Mikey