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

[leroy christophe]

Le 18/09/2014 17:15, Joakim Tjernlund a écrit :
> Christophe Leroy <christophe.leroy@xxxxxx> 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@xxxxxx>
> >
> > ---
> > Changes in v2:
> > - None
> >
> > Changes in v3:
> > - arch/powerpc/mm/fault.c uses the vector number, so make sure it
> understand
> > the new ones.
> >
> >   arch/powerpc/kernel/head_8xx.S | 17 +++++++----------
> >   arch/powerpc/mm/fault.c        |  1 +
> >   2 files changed, 8 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/powerpc/kernel/head_8xx.S
> b/arch/powerpc/kernel/head_8xx.S
> > index 3af6db1..fbe5d10 100644
> > --- a/arch/powerpc/kernel/head_8xx.S
> > +++ b/arch/powerpc/kernel/head_8xx.S
> > @@ -234,15 +234,9 @@ DataAccess:
> >      EXC_XFER_LITE(0x300, handle_page_fault)
> >
> >   /* Instruction access exception.
> > - * This is "never generated" by the MPC8xx.  We jump to it for other
> > - * translation errors.
> > + * This is "never generated" by the MPC8xx.
> >    */
> > -   . = 0x400
> > -InstructionAccess:
> > -   EXCEPTION_PROLOG
> > -   mr   r4,r12
> > -   mr   r5,r9
> > -   EXC_XFER_LITE(0x400, handle_page_fault)
> > +   EXCEPTION(0x400, InstructionAccess, unknown_exception, EXC_XFER_STD)
> >
> >   /* External interrupt */
> >      EXCEPTION(0x500, HardwareInterrupt, do_IRQ, EXC_XFER_LITE)
> > @@ -382,7 +376,7 @@ InstructionTLBMiss:
> >   #endif
> >      mfspr   r10, SPRN_SPRG_SCRATCH2
> >      EXCEPTION_EPILOG_0
> > -   b   InstructionAccess
> > +   b   InstructionTLBError
> >
> >      . = 0x1200
> >   DataStoreTLBMiss:
> > @@ -477,7 +471,10 @@ DataStoreTLBMiss:
> >    */
> >      . = 0x1300
> >   InstructionTLBError:
> > -   b   InstructionAccess
> > +   EXCEPTION_PROLOG
> > +   mr   r4,r12
> > +   mr   r5,r9
> > +   EXC_XFER_LITE(0x1300, handle_page_fault)
> Still don't like that you change the vector number, every other ppc uses
> the
> standard number.
>
> Can you not just lie here(EXC_XFER_LITE(0x400, handle_page_fault))?
> Move the code to InstructionAccess too and let TLBError branch there.
My issue was that if I do EXC_XFER_LITE(0x400, handle_page_fault), I 
can't leave the
    EXCEPTION(0x400, InstructionAccess, unknown_exception, 
EXC_XFER_STD) at address .400
Otherwise, I get twice the same label.

What about the following patch then ? Would this be acceptable ?

@@ -234,15 +234,13 @@ DataAccess:
     EXC_XFER_LITE(0x300, handle_page_fault)

 /* Instruction access exception.
- * This is "never generated" by the MPC8xx.  We jump to it for other
- * translation errors.
+ * This is "never generated" by the MPC8xx.
  */
     . = 0x400
 InstructionAccess:
     EXCEPTION_PROLOG
-    mr    r4,r12
-    mr    r5,r9
-    EXC_XFER_LITE(0x400, handle_page_fault)
+    addi    r3,r1,STACK_FRAME_OVERHEAD
+    EXC_XFER_STD(0x401, unknown_exception)

 /* External interrupt */
     EXCEPTION(0x500, HardwareInterrupt, do_IRQ, EXC_XFER_LITE)
@@ -382,7 +380,7 @@ InstructionTLBMiss:
 #endif
     mfspr    r10, SPRN_SPRG_SCRATCH2
     EXCEPTION_EPILOG_0
-    b    InstructionAccess
+    b    InstructionTLBError

     . = 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)

 /* This is the data TLB error on the MPC8xx.  This could be due to
  * many reasons, including a dirty update to a pte.  We can catch that


> If not I think you should keep the old/current way?
>
> Same for DataTLB Miss/Error
>
> >   /* This is the data TLB error on the MPC8xx.  This could be due to
> >    * many reasons, including a dirty update to a pte.  We can catch that
> > diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
> > index 51ab9e7..4d63c96 100644
> > --- a/arch/powerpc/mm/fault.c
> > +++ b/arch/powerpc/mm/fault.c
> > @@ -526,6 +526,7 @@ void bad_page_fault(struct pt_regs *regs, unsigned
> long address, int sig)
> >         break;
> >      case 0x400:
> >      case 0x480:
> > +   case 0x1300:
> >         printk(KERN_ALERT "Unable to handle kernel paging request for "
> >            "instruction fetch\n");
> >         break;
> > --
> > 2.1.0

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