[PATCH] bookehv: Handle debug exception on guest exit

[Stuart Yoder]

On Thu, Apr 11, 2013 at 1:33 PM, Kumar Gala <galak at kernel.crashing.org> wrote:
>
> On Apr 5, 2013, at 2:53 AM, Bhushan Bharat-R65777 wrote:
>
>> Hi Kumar/Benh,
>>
>> 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.
>>
>> Here is the snapshot for 32 bit (head_booke.h, same will be true for 64 bit):
>>
>> #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 at h;       /* check if exception in vectors */   \
>>        ori     r10,r10,KERNELBASE at l;                                         \
>>        cmplw   r12,r10;                                                      \
>>        blt+    2f;                     /* addr below exception vectors */    \
>>                                                                              \
>>        lis     r10,DebugDebug at h;                                        \
>>        ori     r10,r10,DebugDebug at l;                                            \
>>
>> ^^^^
>>       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?
>>
>>
>>        cmplw   r12,r10;                                                      \
>>        bgt+    2f;                     /* addr above exception vectors */    \
>>
>> 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

Also, it looks like 64-bit already handles this properly with symbols
identifying the
start/end of the vectors (exceptions-64e.S).

Stuart