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

[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.

It's probably not worth another respin, though -- we can just document
right/left justification in the event that we have such a register.

-Scott