Re: [RFC PATCH v3 12/29] KVM: arm64: Make ID_DFR1_EL1 writable

[Eric Auger <eauger@redhat.com>]

On 11/30/21 6:39 AM, Reiji Watanabe wrote:
> Hi Eric,
> 
> On Thu, Nov 25, 2021 at 12:30 PM Eric Auger <eauger@redhat.com> wrote:
>>
>> Hi Reiji,
>>
>> On 11/17/21 7:43 AM, Reiji Watanabe wrote:
>>> This patch adds id_reg_info for ID_DFR1_EL1 to make it writable
>>> by userspace.
>>>
>>> Signed-off-by: Reiji Watanabe <reijiw@google.com>
>>> ---
>>>  arch/arm64/kvm/sys_regs.c | 6 ++++++
>>>  1 file changed, 6 insertions(+)
>>>
>>> diff --git a/arch/arm64/kvm/sys_regs.c b/arch/arm64/kvm/sys_regs.c
>>> index fbd335ac5e6b..dda7001959f6 100644
>>> --- a/arch/arm64/kvm/sys_regs.c
>>> +++ b/arch/arm64/kvm/sys_regs.c
>>> @@ -859,6 +859,11 @@ static struct id_reg_info id_dfr0_el1_info = {
>>>       .get_reset_val = get_reset_id_dfr0_el1,
>>>  };
>>>
>>> +static struct id_reg_info id_dfr1_el1_info = {
>>> +     .sys_reg = SYS_ID_DFR1_EL1,
>>> +     .ftr_check_types = S_FCT(ID_DFR1_MTPMU_SHIFT, FCT_LOWER_SAFE),
>> what about the 0xF value which indicates the MTPMU is not implemented?
> 
> The field is treated as a signed field.
> So, 0xf(== -1) is handled correctly.
> (Does it answer your question?)

yes thanks

Eric
> 
> Thanks,
> Reiji
> 
>>
>> Eric
>>> +};
>>> +
>>>  /*
>>>   * An ID register that needs special handling to control the value for the
>>>   * guest must have its own id_reg_info in id_reg_info_table.
>>> @@ -869,6 +874,7 @@ static struct id_reg_info id_dfr0_el1_info = {
>>>  #define      GET_ID_REG_INFO(id)     (id_reg_info_table[IDREG_IDX(id)])
>>>  static struct id_reg_info *id_reg_info_table[KVM_ARM_ID_REG_MAX_NUM] = {
>>>       [IDREG_IDX(SYS_ID_DFR0_EL1)] = &id_dfr0_el1_info,
>>> +     [IDREG_IDX(SYS_ID_DFR1_EL1)] = &id_dfr1_el1_info,
>>>       [IDREG_IDX(SYS_ID_AA64PFR0_EL1)] = &id_aa64pfr0_el1_info,
>>>       [IDREG_IDX(SYS_ID_AA64PFR1_EL1)] = &id_aa64pfr1_el1_info,
>>>       [IDREG_IDX(SYS_ID_AA64DFR0_EL1)] = &id_aa64dfr0_el1_info,
>>>
>>
> 

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