Re: [Xen-devel] [PATCH] xen: Bump __XEN_LATEST_INTERFACE_VERSION__ to 0x00040700

[Razvan Cojocaru <rcojocaru@xxxxxxxxxxxxxxx>]

On 09/30/2015 06:39 PM, Jan Beulich wrote:
>>>> On 30.09.15 at 17:27, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>> On 09/30/2015 06:23 PM, Jan Beulich wrote:
>>>>>> On 30.09.15 at 17:16, <rcojocaru@xxxxxxxxxxxxxxx> wrote:
>>>> VM_EVENT_FLAG_SET_REGISTERS and xc_monitor_emulate_each_rep() are
>>>> not available in Xen 4.6, hence the bump.
>>>
>>> I don't follow: These are additions, not changes that require
>>> consumers to adapt their code.
>>
>> I have code that checks for __XEN_LATEST_INTERFACE_VERSION__ and if it
>> is 0x00040700 then it uses xc_monitor_emulate_each_rep(), otherwise it
>> knows it can't - I thought that consumers that want to make use of the
>> latest API should be able to tell that they're allowed to do so.
>>
>> But if the Xen convention is to only bump it when the interface is no
>> longer backward compatible then I've misunderstood (in which case, sorry
>> for the noise, and also, is there another way to tell which Xen version
>> I'm compiling against?).
> 
> Just check for the relevant #define to be there.

That does work for VM_EVENT_FLAG_SET_REGISTERS in this case, but it
wouldn't have worked if the only addition would have been
xc_monitor_emulate_each_rep(). I like the XEN_VERSION and XEN_SUBVERSION
#defines in compile.h, but those don't make it into the public headers
(that end up in dist/install/usr/include after make dist).

But yes, in this case that #define is helpful, and then with autotools
or something similar libxc can be checked for xc_monitor_emulate_each_rep().

Again, sorry for the noise and thanks for the help.


Thanks,
Razvan

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