linux-kernel - Re: [PATCH v3 03/21] powerpc/8xx: exception InstructionAccess does not exist on MPC8xx

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Message-ID: <OFFF48B453.8913C6B0-ONC1257D57.006DED24-C1257D57.006E0FCC@transmode.se>
Date:	Thu, 18 Sep 2014 22:02:09 +0200
From:	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>
To:	christophe leroy <christophe.leroy@....fr>
Cc:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Paul Mackerras <paulus@...ba.org>, scottwood@...escale.com
Subject: Re: [PATCH v3 03/21] powerpc/8xx: exception InstructionAccess does not
 exist on MPC8xx

christophe leroy <christophe.leroy@....fr> wrote on 2014/09/18 21:11:01:
> 
> 
> Le 18/09/2014 20:12, Joakim Tjernlund a écrit :
> > leroy christophe <christophe.leroy@....fr> wrote on 2014/09/18 
18:42:14:
> >
> >> Le 18/09/2014 17:15, Joakim Tjernlund a écrit :
> >>> Christophe Leroy <christophe.leroy@....fr> wrote on 2014/09/17
> > 18:36:57:
> >>>> Exception InstructionAccess does not exist on MPC8xx. No need to
> > branch
> >>> there from somewhere else.
> >>>> Handling can be done directly in InstructionTLBError Exception.
> >>>>
> >>>> Signed-off-by: Christophe Leroy <christophe.leroy@....fr>
> >>        . = 0x1200
> >>    DataStoreTLBMiss:
> >> @@ -477,7 +475,11 @@ DataStoreTLBMiss:
> >>     */
> >>        . = 0x1300
> >>    InstructionTLBError:
> >> -    b    InstructionAccess
> >> +    EXCEPTION_PROLOG
> >> +    mr    r4,r12
> >> +    mr    r5,r9
> >> +    /* 0x400 is InstructionAccess exception, needed by 
bad_page_fault()
> > */
> >> +    EXC_XFER_LITE(0x400, handle_page_fault)
> > You should have the code in TLBMiss and have the TLBError branch there 
as
> > that is the common case.
> As far as I remember, I tried it already but we don't have enough space 
> in TLBmiss for that. We can only have 40 instructions.

Do your other optimizations first, then you might have space :)

 Jocke
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