Re: [Qemu-devel] [PATCH v2 05/14] target/arm/helper: zcr: Add build bug next to value range assumption

[Auger Eric]

Hi,

On 6/26/19 3:58 PM, Andrew Jones wrote:
> On Wed, Jun 26, 2019 at 03:40:11PM +0200, Auger Eric wrote:
>> Hi,
>>
>> On 6/26/19 3:28 PM, Andrew Jones wrote:
>>> On Wed, Jun 26, 2019 at 12:01:10PM +0200, Auger Eric wrote:
>>>> Hi Drew,
>>>>
>>>> On 6/21/19 6:34 PM, Andrew Jones wrote:
>>>>> Suggested-by: Dave Martin <address@hidden>
>>>>> Signed-off-by: Andrew Jones <address@hidden>
>>>>> ---
>>>>>  target/arm/helper.c | 1 +
>>>>>  1 file changed, 1 insertion(+)
>>>>>
>>>>> diff --git a/target/arm/helper.c b/target/arm/helper.c
>>>>> index df4276f5f6ca..edba94004e0b 100644
>>>>> --- a/target/arm/helper.c
>>>>> +++ b/target/arm/helper.c
>>>>> @@ -5319,6 +5319,7 @@ static void zcr_write(CPUARMState *env, const 
>>>>> ARMCPRegInfo *ri,
>>>>>      int new_len;
>>>>>  
>>>>>      /* Bits other than [3:0] are RAZ/WI.  */
>>>>> +    QEMU_BUILD_BUG_ON(ARM_MAX_VQ > 16);
>>>> Can you document in the commit message why this check is critical?
>>>
>>> Sure. I can copy+paste the email subject into the commit message :-)
>> Well that's not what I asked for. Are you enforcing an architectural
>> maximum of 2048 bits or is the limitation due to some data structs in
>> the existing code, ... For a non expert reviewer as I am it is not
>> totally obvious.
> 
> How's this for the commit message
> 
>     The current implementation of ZCR_ELx matches the architecture, only
>     implementing the lower four bits, with the rest RAZ/WI. This puts
>     a strict limit on ARM_MAX_VQ of 16. Make sure we don't let ARM_MAX_VQ
>     grow without a corresponding update here.
Yep perfect. Thanks

Reviewed-by: Eric Auger <address@hidden>

Eric

> 
> Thanks,
> drew
> 
>>
>> Thanks
>>
>> Eric
>>>
>>> drew
>>>
>>>>
>>>> Thanks
>>>>
>>>> Eric
>>>>>      raw_write(env, ri, value & 0xf);
>>>>>  
>>>>>      /*
>>>>>
>>>>
>