[libvirt] [PATCH v2 0/9] Incremental Backup API additions

[Eric Blake]

On 10/12/18 11:28 AM, Jiri Denemark wrote:

>> Since I will be demonstrating the use of this API at the KVM Forum,
>> I would really like a decision on whether we can commit the API
>> into libvirt now, even if we have to wait for the qemu implementation
> 
> No we can't. We did it once in the past and although I don't remember
> the exact details I remember it turned out to be a bad idea. Also
> pushing an API with no implementation doesn't really make sense since
> the API is unusable until it is implemented in some hypervisor driver.

You wouldn't, by chance, be thinking of the fact that 
virDomainBlockCopy() landed in 1.2.8, but didn't get implemented until 
1.2.9?  (Yes, that one also has my name suspiciously tied to it.  How 
come I always seem to be implementing APIs that downstream wants sooner 
than upstream is ready to commit to?)

> 
>> of the API until qemu stabilizes its interfaces (also, having the
>> libvirt API in place gives qemu an incentive to drop the x- prefix
>> sooner rather than later).
> 
> The presence of public API in libvirt gives no clue to QEMU engineers
> that their API provides everything needed and x- prefix should be
> dropped. Only working patches implementing the libvirt APIs for QEMU can
> provide such feedback to QEMU developers.

My v3 is demonstration that QEMU is on the right track for providing 
everything I needed for a rudimentary implementation; the qemu 
implementation can be further fine-tuned as it waits for qemu to polish 
its interface.

-- 
Eric Blake, Principal Software Engineer
Red Hat, Inc.           +1-919-301-3266
Virtualization:  qemu.org | libvirt.org