Re: [Qemu-devel] [PATCH for 2.1 00/97] VMState simplification (massive)

[Juan Quintela <quintela@redhat.com>]

"Dr. David Alan Gilbert" <dgilbert@redhat.com> wrote:
> * Juan Quintela (quintela@redhat.com) wrote:
>> Hi
>> 
>>   Look at the diffstat.  Almost all the additions are at
>> test-vmstate.c. That is the reason why it is called a simplification.
>> 
>> What this series does:
>> - peter removal of version_minimum_id_old field when not needed (Peter)
>> - cleanup: based on the previous one, I removed all the unneeded
>>   the uses on the tree.  This should make your compiles
>>   a couple of nanoseconds faster.
>> - once there, fixed the indentation of the .fields line, to a canonical
>>     .fields = (VMStateField[])
>> - mst simplifications for vmstate engine
>> 
>> And now, the big cleanup.
>> - Patches only do one thing, to make easy the review.
>> 
>> - Added test for all VMSTATE_FOO() definitions
>>   (well, I am lying, VMSTATE_STRUCT* are still missing, will come soon)
>> - We had two ways to make a field optional
>>    VMSTATE_INT64_V(field, state, version)
>>   and
>>    VMSTATE_INT64_TEST(field, state, test)
>> 
>>   We can do the version one with one test like:
>> 
>> static inline bool vmstate_5_plus(void *opaque, int version_id)
>> {
>>     return version_id >= 5;
>> }
>> 
>>   and then change:
>>   VMSTATE_INT64_V(field, state, 5);
>> 
>>   into
>>   VMSTATE_INT64_TEST(field, state, vmstate_5_plus);
>
> I'm not sure if I like this; while I'm OK with the idea of changing the
> implementation of VMSTATE_INT64_V to use that function trick internally,
> it seems like we're discouraging providing easy to parse/record versionining
> info out of the tree.

That information is not exported Today.  And if we want to export them,
export v = 5 or test == vmstat_5_plus is exactly the same dificulty.
The information is still there, what has changed is the removal of one
mechanism.

#define VMSTATE_UINT64_V(field, state, X) \
     VMSTATE_UINT64_TEST(field, state, vmstate_##X##_plus)

The same that we could do for maintaining the macro, we can do to export
the information to whatever format we want.  I just wanted to remove one
of the mechanism (the less powerful one).

Later, Juan.