Re: [PATCH] bookehv: Handle debug exception on guest exit

[Kumar Gala <galak@kernel.crashing.org>]

On Apr 5, 2013, at 2:53 AM, Bhushan Bharat-R65777 wrote:

> Hi Kumar/Benh,
>=20
> After further looking into the code I think that if we correct the =
vector range below in DebugDebug handler then we do not need the change =
I provided in this patch.
>=20
> Here is the snapshot for 32 bit (head_booke.h, same will be true for =
64 bit):
>=20
> #define DEBUG_DEBUG_EXCEPTION                                          =
       \
>        START_EXCEPTION(DebugDebug);                                    =
      \
>        DEBUG_EXCEPTION_PROLOG;                                         =
      \
>                                                                        =
      \
>        /*                                                              =
      \
>         * If there is a single step or branch-taken exception in an    =
      \
>         * exception entry sequence, it was probably meant to apply to  =
      \
>         * the code where the exception occurred (since exception entry =
      \
>         * doesn't turn off DE automatically).  We simulate the effect  =
      \
>         * of turning off DE on entry to an exception handler by =
turning      \
>         * off DE in the DSRR1 value and clearing the debug status.     =
      \
>         */                                                             =
      \
>        mfspr   r10,SPRN_DBSR;          /* check single-step/branch =
taken */  \
>        andis.  r10,r10,(DBSR_IC|DBSR_BT)@h;                            =
      \
>        beq+    2f;                                                     =
      \
>                                                                        =
      \
>        lis     r10,KERNELBASE@h;       /* check if exception in =
vectors */   \
>        ori     r10,r10,KERNELBASE@l;                                   =
      \
>        cmplw   r12,r10;                                                =
      \
>        blt+    2f;                     /* addr below exception vectors =
*/    \
>                                                                        =
      \
>        lis     r10,DebugDebug@h;                                       =
 \
>        ori     r10,r10,DebugDebug@l;                                   =
         \
>=20
> ^^^^
> 	Here we assume all exception vector ends at DebugDebug, which is =
not correct.
> 	We probably should get proper end by using some start_vector and =
end_vector lebels
> 	or at least use end at Ehvpriv (which is last defined in =
head_fsl_booke.S for PowerPC. Is that correct?
>=20
> =09
>        cmplw   r12,r10;                                                =
      \
>        bgt+    2f;                     /* addr above exception vectors =
*/    \
>=20
> Thanks
> -Bharat

I talked to Stuart and this general approach is good.  Just make sure to =
update both head_44x.S and head_fsl_booke.S.  Plus do this for both =
DEBUG_CRIT_EXCEPTION & DEBUG_DEBUG_EXCEPTION

- k=