Re: [Xen-devel] [PATCH v2 03/25] arm/altp2m: Add struct vttbr.

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

On 08/06/2016 03:20 PM, Julien Grall wrote:
>
>
> On 06/08/2016 09:54, Sergej Proskurin wrote:
>> Hi Julien,
>
> Hello Sergej,
>
>> On 08/04/2016 06:15 PM, Julien Grall wrote:
>>>
>>>
>>> On 04/08/16 17:11, Sergej Proskurin wrote:
>>>>>>> diff --git a/xen/include/asm-arm/processor.h
>>>>>>> b/xen/include/asm-arm/processor.h
>>>>>>> index 15bf890..f8ca18c 100644
>>>>>>> --- a/xen/include/asm-arm/processor.h
>>>>>>> +++ b/xen/include/asm-arm/processor.h
>>>>>>> @@ -529,6 +529,22 @@ union hsr {
>>>>>>>
>>>>>>>
>>>>>>>  };
>>>>>>> +
>>>>>>> +/* VTTBR: Virtualization Translation Table Base Register */
>>>>>>> +struct vttbr {
>>>>>>> +    union {
>>>>>>> +        struct {
>>>>>>> +            u64 baddr :40, /* variable res0: from 0-(x-1) bit */
>>>>>>
>>>>>> As mentioned on the previous series, this field is 48 bits for ARMv8
>>>>>> (see ARM D7.2.102 in DDI 0487A.j).
>>>>>>
>>>>
>>>> I must have missed it during refactoring. At this point, I will
>>>> distinguish between __arm__ and __aarch64__, thank you.
>>>
>>> After reading this series I see no point having this union. So I would
>>> much prefer to see this patch dropped.
>>>
>>
>> I can do that. However, I do not understand why we would prefer using
>> error prone bit operations for VTTBR initialization instead of having a
>> unified and simple way of initializing and using the VTTBR including the
>> VMID and the root table address.
>
> The VTTBR only needs to be initialized in one place and we don't care
> accessing the fields. So I don't see the benefit to introduce a
> structure for that.
>

Ok. I will drop this patch.

Best regards,
~Sergej

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