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Date: Tue, 30 Mar 2010 15:47:05 +0530
From: "K.Prasad" <prasad@linux.vnet.ibm.com>
To: Paul Mackerras <paulus@samba.org>
Subject: Re: [RFC Patch 1/2] PPC64-HWBKPT: Disable interrupts for data
	breakpoint exceptions
Message-ID: <20100330101705.GB14734@in.ibm.com>
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	<20100330052442.GB12619@drongo>
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On Tue, Mar 30, 2010 at 04:24:42PM +1100, Paul Mackerras wrote:
> On Tue, Mar 23, 2010 at 07:37:02PM +0530, K.Prasad wrote:
> 
> > Index: linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S
> > ===================================================================
> > --- linux-2.6.ppc64_test.orig/arch/powerpc/kernel/exceptions-64s.S
> > +++ linux-2.6.ppc64_test/arch/powerpc/kernel/exceptions-64s.S
> > @@ -735,6 +735,9 @@ _STATIC(do_hash_page)
> >  	std	r3,_DAR(r1)
> >  	std	r4,_DSISR(r1)
> >  
> > +	andis.  r0,r4,0x0040		/* Data Address Breakpoint match? */
> 
> Minor comment: why not DSISR_DABRMATCH@h instead of 0x0040?
>

Sure...I didn't realise that the upper 16-bits could be extracted as
shown above....I've implemented the suggestion in the next version of
the patch sent here:
linuxppc-dev message-id:20100330095809.GA14403@in.ibm.com.

> > +	bne-    handle_dabr_fault
> > +
> >  	andis.	r0,r4,0xa450		/* weird error? */
> >  	bne-	handle_page_fault	/* if not, try to insert a HPTE */
> >  BEGIN_FTR_SECTION
> > @@ -823,6 +826,15 @@ END_FW_FTR_SECTION_IFCLR(FW_FEATURE_ISER
> >  	bl	.raw_local_irq_restore
> >  	b	11f
> >  
> > +/* We have a data breakpoint exception - handle it */
> > +handle_dabr_fault:
> > +	/* Populate the pt_regs structure */
> 
> Another minor comment: that comment isn't accurate since you're not
> putting anything in the pt_regs, just getting arguments to do_dabr
> from it.
>

Thanks for pointing it out...it has been removed.

Thanks,
K.Prasad