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

[Sergej Proskurin <proskurin@xxxxxxxxxxxxx>]

Hi Julien,


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.

Best regards,
~Sergej

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