Re: [Qemu-devel] [PATCH v2 7/7] target-arm: Call the pmccntr_sync function when swapping ELs

[Peter Crosthwaite]

On Sat, Aug 2, 2014 at 1:35 AM, Peter Maydell <address@hidden> wrote:
> On 26 June 2014 06:02, Alistair Francis <address@hidden> wrote:
>> Call the new pmccntr_sync() function when there is a possibility
>> of swapping ELs (I.E. when there is an exception)
>>
>> Signed-off-by: Alistair Francis <address@hidden>
>> ---
>>
>>  target-arm/helper-a64.c |    5 +++++
>>  target-arm/helper.c     |    7 +++++++
>>  target-arm/op_helper.c  |    6 ++++++
>>  3 files changed, 18 insertions(+), 0 deletions(-)
>>
>> diff --git a/target-arm/helper-a64.c b/target-arm/helper-a64.c
>> index 2b4ce6a..b61174f 100644
>> --- a/target-arm/helper-a64.c
>> +++ b/target-arm/helper-a64.c
>> @@ -446,6 +446,8 @@ void aarch64_cpu_do_interrupt(CPUState *cs)
>>      target_ulong addr = env->cp15.vbar_el[1];
>>      int i;
>>
>> +    pmccntr_sync(env);
>> +
>>      if (arm_current_pl(env) == 0) {
>>          if (env->aarch64) {
>>              addr += 0x400;
>> @@ -484,6 +486,7 @@ void aarch64_cpu_do_interrupt(CPUState *cs)
>>          addr += 0x100;
>>          break;
>>      default:
>> +        pmccntr_sync(env);
>>          cpu_abort(cs, "Unhandled exception 0x%x\n", cs->exception_index);
>>      }
>>
>> @@ -511,4 +514,6 @@ void aarch64_cpu_do_interrupt(CPUState *cs)
>>
>>      env->pc = addr;
>>      cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
>> +
>> +    pmccntr_sync(env);
>>  }
>> diff --git a/target-arm/helper.c b/target-arm/helper.c
>> index e78c5a7..f05d912 100644
>> --- a/target-arm/helper.c
>> +++ b/target-arm/helper.c
>> @@ -3457,6 +3457,8 @@ void arm_cpu_do_interrupt(CPUState *cs)
>>
>>      assert(!IS_M(env));
>>
>> +    pmccntr_sync(env);
>> +
>>      arm_log_exception(cs->exception_index);
>>
>>      /* TODO: Vectored interrupt controller.  */
>> @@ -3487,6 +3489,7 @@ void arm_cpu_do_interrupt(CPUState *cs)
>>                    && (env->uncached_cpsr & CPSR_M) != ARM_CPU_MODE_USR) {
>>                  env->regs[0] = do_arm_semihosting(env);
>>                  qemu_log_mask(CPU_LOG_INT, "...handled as semihosting 
>> call\n");
>> +                pmccntr_sync(env);
>>                  return;
>>              }
>>          }
>> @@ -3505,6 +3508,7 @@ void arm_cpu_do_interrupt(CPUState *cs)
>>                  env->regs[15] += 2;
>>                  env->regs[0] = do_arm_semihosting(env);
>>                  qemu_log_mask(CPU_LOG_INT, "...handled as semihosting 
>> call\n");
>> +                pmccntr_sync(env);
>>                  return;
>>              }
>>          }
>> @@ -3548,6 +3552,7 @@ void arm_cpu_do_interrupt(CPUState *cs)
>>          offset = 4;
>>          break;
>>      default:
>> +        pmccntr_sync(env);
>>          cpu_abort(cs, "Unhandled exception 0x%x\n", cs->exception_index);
>>          return; /* Never happens.  Keep compiler happy.  */
>>      }
>> @@ -3580,6 +3585,8 @@ void arm_cpu_do_interrupt(CPUState *cs)
>>      env->regs[14] = env->regs[15] + offset;
>>      env->regs[15] = addr;
>>      cs->interrupt_request |= CPU_INTERRUPT_EXITTB;
>> +
>> +    pmccntr_sync(env);
>>  }
>>
>>  /* Check section/page access permissions.
>> diff --git a/target-arm/op_helper.c b/target-arm/op_helper.c
>> index 9c1ef52..07ab30b 100644
>> --- a/target-arm/op_helper.c
>> +++ b/target-arm/op_helper.c
>> @@ -376,6 +376,8 @@ void HELPER(exception_return)(CPUARMState *env)
>>      uint32_t spsr = env->banked_spsr[spsr_idx];
>>      int new_el, i;
>>
>> +    pmccntr_sync(env);
>> +
>>      if (env->pstate & PSTATE_SP) {
>>          env->sp_el[cur_el] = env->xregs[31];
>>      } else {
>> @@ -418,6 +420,8 @@ void HELPER(exception_return)(CPUARMState *env)
>>          env->pc = env->elr_el[cur_el];
>>      }
>>
>> +    pmccntr_sync(env);
>> +
>>      return;
>>
>>  illegal_return:
>> @@ -433,6 +437,8 @@ illegal_return:
>>      spsr &= PSTATE_NZCV | PSTATE_DAIF;
>>      spsr |= pstate_read(env) & ~(PSTATE_NZCV | PSTATE_DAIF);
>>      pstate_write(env, spsr);
>> +
>> +    pmccntr_sync(env);
>>  }
>
> This feels way too fragile to me to be scattering these sync
> calls all over the place like this. We need to find a better
> approach than this.
>

If we could consolidate all the code paths that actually switch el
(both ways) into a helper fn we could then add the pmccntr
el-switching side effects (i.e. the sync) to that helper once. Would
you accept such an approach?

Regards,
Peter

> thanks
> -- PMM
>