Re: [Qemu-devel] [PATCH 5/6] target-arm: Implement MDCR_EL2.TDA and MDCR_EL2.TDA traps

[Sergey Fedorov <serge.fdrv@gmail.com>]

On 08.02.2016 19:38, Peter Maydell wrote:
> On 8 February 2016 at 16:31, Sergey Fedorov <serge.fdrv@gmail.com> wrote:
>> One of the MDCR_EL2's should be MDCR_EL3 instead.
> Oops, yes :-)
>
>> On 05.02.2016 19:45, Peter Maydell wrote:
>>> Implement the debug register traps controlled by MDCR_EL2.TDA
>>> and MDCR_EL3.TDA.
>>>
>>> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
>>> ---
>>>  target-arm/helper.c | 39 ++++++++++++++++++++++++++++++---------
>>>  1 file changed, 30 insertions(+), 9 deletions(-)
>>>
>>> diff --git a/target-arm/helper.c b/target-arm/helper.c
>>> index 8c2adbc..064b415 100644
>>> --- a/target-arm/helper.c
>>> +++ b/target-arm/helper.c
>>> @@ -420,6 +420,24 @@ static CPAccessResult access_tdra(CPUARMState *env, const ARMCPRegInfo *ri,
>>>      return CP_ACCESS_OK;
>>>  }
>>>
>>> +/* Check for traps to general debug registers, which are controlled
>>> + * by MDCR_EL2.TDA for EL2 and MDCR_EL3.TDA for EL3.
>>> + */
>>> +static CPAccessResult access_tda(CPUARMState *env, const ARMCPRegInfo *ri,
>>> +                                  bool isread)
>>> +{
>>> +    int el = arm_current_el(env);
>>> +
>>> +    if (el < 2 && (env->cp15.mdcr_el2 & MDCR_TDA)
>>> +        && !arm_is_secure_below_el3(env)) {
>>> +        return CP_ACCESS_TRAP_EL2;
>>> +    }
>>> +    if (el < 3 && (env->cp15.mdcr_el3 & MDCR_TDA)) {
>>> +        return CP_ACCESS_TRAP_EL3;
>>> +    }
>>> +    return CP_ACCESS_OK;
>>> +}
>>> +
>>>  static void dacr_write(CPUARMState *env, const ARMCPRegInfo *ri, uint64_t value)
>>>  {
>>>      ARMCPU *cpu = arm_env_get_cpu(env);
>>> @@ -3385,7 +3403,8 @@ static const ARMCPRegInfo el3_no_el2_cp_reginfo[] = {
>>>        .access = PL2_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
>>>      { .name = "MDCR_EL2", .state = ARM_CP_STATE_BOTH,
>>>        .opc0 = 3, .opc1 = 4, .crn = 1, .crm = 1, .opc2 = 1,
>>> -      .access = PL2_RW, .type = ARM_CP_CONST, .resetvalue = 0 },
>>> +      .access = PL2_RW, .accessfn = access_tda,
>>> +      .type = ARM_CP_CONST, .resetvalue = 0 },
>>>      { .name = "HPFAR_EL2", .state = ARM_CP_STATE_BOTH,
>>>        .opc0 = 3, .opc1 = 4, .crn = 6, .crm = 0, .opc2 = 4,
>>>        .access = PL2_RW, .accessfn = access_el3_aa32ns_aa64any,
>>> @@ -3804,7 +3823,7 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
>>>      /* Monitor debug system control register; the 32-bit alias is DBGDSCRext. */
>>>      { .name = "MDSCR_EL1", .state = ARM_CP_STATE_BOTH,
>>>        .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 2, .opc2 = 2,
>>> -      .access = PL1_RW,
>>> +      .access = PL1_RW, .accessfn = access_tda,
>>>        .fieldoffset = offsetof(CPUARMState, cp15.mdscr_el1),
>>>        .resetvalue = 0 },
>>>      /* MDCCSR_EL0, aka DBGDSCRint. This is a read-only mirror of MDSCR_EL1.
>>> @@ -3813,7 +3832,7 @@ static const ARMCPRegInfo debug_cp_reginfo[] = {
>>>      { .name = "MDCCSR_EL0", .state = ARM_CP_STATE_BOTH,
>>>        .cp = 14, .opc0 = 2, .opc1 = 0, .crn = 0, .crm = 1, .opc2 = 0,
>>>        .type = ARM_CP_ALIAS,
>>> -      .access = PL1_R,
>>> +      .access = PL1_R, .accessfn = access_tda,
>> From ARMv8 ARM rev. A.h: "If MDSCR_EL1.TDCC==1, EL0 read accesses to
>> this register are trapped to EL1." But it seems like we just don't
>> implement "Config-RO for EL0" so far.
> Yes. There's a comment about this, though it's just outside the
> context region that diff has produced.
>
>> Maybe it's worth to implement a
>> separate function for checks controlled by MDSCR_EL1.TDCC?
> I think that's a separate issue from the EL2/EL3 traps and
> should go in its own patch. This series is just trying to get
> EL3 right.

Okay, with fixed subject:

Reviewed-by: Sergey Fedorov <serge.fdrv@gmail.com>

Kind regards,
Sergey