Re: [PATCH] KVM: PPC: Add generic single register ioctls

[Scott Wood <scottwood@freescale.com>]

On 01/09/2012 02:11 PM, Alexander Graf wrote:
> 
> 
> Am 09.01.2012 um 20:07 schrieb Scott Wood <scottwood@freescale.com>:
> 
>> On 01/06/2012 06:52 PM, Alexander Graf wrote:
>>>
>>>
>>> On 06.01.2012, at 20:32, Scott Wood <scottwood@freescale.com> wrote:
>>>
>>>> On 01/05/2012 10:15 PM, Alexander Graf wrote:
>>>>
>>>>> +/*
>>>>> + * Architecture specific registers are to be defined in arch headers and
>>>>> + * ORed with the arch identifier.
>>>>> + */
>>>>> +#define KVM_REG_PPC        0x1000000000000000ULL
>>>>> +#define KVM_REG_X86        0x2000000000000000ULL
>>>>> +#define KVM_REG_IA64        0x3000000000000000ULL
>>>>> +#define KVM_REG_ARM        0x4000000000000000ULL
>>>>> +#define KVM_REG_S390        0x5000000000000000ULL
>>>>> +
>>>>> +#define KVM_REG_SIZE_SHIFT    52
>>>>> +#define KVM_REG_SIZE_MASK    0x00f0000000000000ULL
>>>>> +#define KVM_REG_SIZE_U8        0x0000000000000000ULL
>>>>> +#define KVM_REG_SIZE_U16    0x0010000000000000ULL
>>>>> +#define KVM_REG_SIZE_U32    0x0020000000000000ULL
>>>>> +#define KVM_REG_SIZE_U64    0x0030000000000000ULL
>>>>> +#define KVM_REG_SIZE_U128    0x0040000000000000ULL
>>>>> +#define KVM_REG_SIZE_U256    0x0050000000000000ULL
>>>>> +#define KVM_REG_SIZE_U512    0x0060000000000000ULL
>>>>> +#define KVM_REG_SIZE_U1024    0x0070000000000000ULL
>>>>
>>>> Why not just encode directly as number of bytes?
>>>
>>> Because this is 1 << n bytes :)
>>
>> Some registers may not be a power-of-2 number of bytes (e.g. x86 segment
>> descriptors), and we've got plenty of space to spare in the id.
> 
> If they're not a power of 2, we can still bmp it to the next power of 2 size, no?

Yes, that's what I meant by it not being a huge deal and documenting
whether the padding is on the right or the left.  Just seems a little
more awkward than necessary, given that we have room to encode it as a
plain linear size.

-Scott