linux-kernel - Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused the exception.

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Message-Id: <20170619175919.GD5845@ram.oc3035372033.ibm.com>
Date:   Mon, 19 Jun 2017 10:59:19 -0700
From:   Ram Pai <linuxram@...ibm.com>
To:     Michael Ellerman <mpe@...erman.id.au>
Cc:     linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
        benh@...nel.crashing.org, paulus@...ba.org,
        khandual@...ux.vnet.ibm.com, aneesh.kumar@...ux.vnet.ibm.com,
        bsingharora@...il.com, dave.hansen@...el.com, hbabu@...ibm.com
Subject: Re: [RFC v2 10/12] powerpc: Read AMR only if pkey-violation caused
 the exception.

On Mon, Jun 19, 2017 at 09:06:13PM +1000, Michael Ellerman wrote:
> Ram Pai <linuxram@...ibm.com> writes:
> 
> > Signed-off-by: Ram Pai <linuxram@...ibm.com>
> > ---
> >  arch/powerpc/kernel/exceptions-64s.S | 16 ++++++++++------
> >  1 file changed, 10 insertions(+), 6 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/exceptions-64s.S b/arch/powerpc/kernel/exceptions-64s.S
> > index 8db9ef8..a4de1b4 100644
> > --- a/arch/powerpc/kernel/exceptions-64s.S
> > +++ b/arch/powerpc/kernel/exceptions-64s.S
> > @@ -493,13 +493,15 @@ EXC_COMMON_BEGIN(data_access_common)
> >  	ld	r12,_MSR(r1)
> >  	ld	r3,PACA_EXGEN+EX_DAR(r13)
> >  	lwz	r4,PACA_EXGEN+EX_DSISR(r13)
> > +	std	r3,_DAR(r1)
> > +	std	r4,_DSISR(r1)
> >  #ifdef CONFIG_PPC64_MEMORY_PROTECTION_KEYS
> > +	andis.  r0,r4,DSISR_KEYFAULT@h /* save AMR only if its a key fault */
> > +	beq+	1f
> 
> This seems to be incremental on top of one of your other patches.
> 
> But I don't see why, can you please just squash this into whatever patch
> adds this code in the first place.

It was an optimization added later. But yes it can be squashed into an
earlier patch.

RP