Re: [Qemu-devel] [PATCH v2 3/4] target-arm: kvm - support for single step

["Alex Bennée" <alex.bennee@linaro.org>]

Peter Maydell <peter.maydell@linaro.org> writes:

> On 31 March 2015 at 16:40, Alex Bennée <alex.bennee@linaro.org> wrote:
>> This adds support for single-step. There isn't much to do on the QEMU
>> side as after we set-up the request for single step via the debug ioctl
>> it is all handled within the kernel.
>>
>> Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
>>
>> ---
>> v2
>>   - convert to using HSR_EC
>>
>> diff --git a/target-arm/kvm.c b/target-arm/kvm.c
>> index 290c1fe..ae0f8b2 100644
>> --- a/target-arm/kvm.c
>> +++ b/target-arm/kvm.c
>> @@ -475,6 +475,7 @@ void kvm_arch_post_run(CPUState *cs, struct kvm_run *run)
>>  */
>>
>>  #define HSR_EC_SHIFT            26
>> +#define HSR_EC_SOFT_STEP        0x32
>>  #define HSR_EC_SW_BKPT          0x3c
>
> We already include internals.h in this file, so can you just use
> the EC_* constants and ARM_EL_EC_SHIFT rather than defining
> new ones? (Applies for patch 1 as well.)
>
>>  static int kvm_handle_debug(CPUState *cs, struct kvm_run *run)
>> @@ -483,6 +484,13 @@ static int kvm_handle_debug(CPUState *cs, struct kvm_run *run)
>>      int hsr_ec = arch_info->hsr >> HSR_EC_SHIFT;
>>
>>      switch (hsr_ec) {
>> +    case HSR_EC_SOFT_STEP:
>> +        if (cs->singlestep_enabled) {
>> +            return true;
>> +        } else {
>> +            error_report("Came out of SINGLE STEP when not enabled");
>
> This can only happen if there's a kernel bug, right?

Sure. Should we report it differently? abort() out?

>
>> +        }
>> +        break;
>>      case HSR_EC_SW_BKPT:
>>          if (kvm_find_sw_breakpoint(cs, arch_info->pc)) {
>>              return true;
>> @@ -542,6 +550,9 @@ int kvm_arch_on_sigbus(int code, void *addr)
>>
>>  void kvm_arch_update_guest_debug(CPUState *cs, struct kvm_guest_debug *dbg)
>>  {
>> +    if (cs->singlestep_enabled) {
>> +        dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_SINGLESTEP;
>> +    }
>>      if (kvm_sw_breakpoints_active(cs)) {
>>          dbg->control |= KVM_GUESTDBG_ENABLE | KVM_GUESTDBG_USE_SW_BP;
>>      }
>> --
>> 2.3.4
>>
>
>
> thanks
> -- PMM

-- 
Alex Bennée