Re: [Xen-devel] [PATCH v7 04/11] public: xen.h: add definitions for UUID handling

[George Dunlap <george.dunlap@xxxxxxxxxx>]

On 10/05/2017 03:50 PM, Volodymyr Babchuk wrote:
> Hi Konrad,
> 
> On 05.10.17 16:03, Konrad Rzeszutek Wilk wrote:
>> On Thu, Oct 05, 2017 at 12:00:20AM +0300, Volodymyr Babchuk wrote:
>>> Added type xen_uuid_t. This type represents UUID as an array of 16
>>> bytes in big endian format.
>>>
>>> Added macro XEN_DEFINE_UUID that constructs UUID in the usual way:
>>>
>>>   XEN_DEFINE_UUID(0x00112233, 0x4455, 0x6677, 0x8899,
>>>         0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff)
>>>
>>> will construct UUID 00112233-4455-6677-8899-aabbccddeeff presented as
>>>   {0x00, 0x11, 0x22, 0x33, 0x44, 0x55, 0x66, 0x77, 0x88,
>>>    0x99, 0xaa, 0xbb, 0xcc, 0xdd, 0xee, 0xff}
>>>
>>> NB: This is compatible with Linux kernel and with libuuid, but it is not
>>> compatible with Microsoft, as they use mixed-endian encoding (some
>>> components are little-endian, some are big-endian).
>>
>> Oh boy. What a mess.
>>
>> Do we care about Microsoft for this or is this more for information
>> purpose?
> This is for information. Problem is that XEN already defines EFI_GUID
> which uses MS-style encoding. It is used in EFI code only, but I think
> it is worth to explain differences.
> There was discussion at [1]
> [...]
> 
> [1] http://markmail.org/message/cawi6f33spqg4hf5

So did you perhaps mean to say something like this:

"NB: We define a new structure here rather than re-using EFI_GUID.
EFI_GUID uses a Microsoft-style encoding which, among other things,
mixes little-endian and big-endian.  The structure defined in this
patch, unlike EFI_GUID, is compatible with the Linux kernel and libuuid."

 -George

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