Re: [PATCH RFC v2 6/6] KVM: introduce a new API for getting dirty bitmaps

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(2010/04/20 20:33), Alexander Graf wrote:

-#define KVM_API_VERSION 12
+#define KVM_API_VERSION 13

Is there a way to keep both interfaces around for some time at least? I'd prefer the API version not to change if not _really_ necessary.

To enable the new dirty mapping you could for example use KVM_CAP_ENABLE_CAP :-).

Thanks, I did not know what is the appropriate way for this kind of change.

I just read the comments in the kvm.h and thought I had to update the number whenever
I added some entries to kvm.h .

The rule of thumb is:

KVM_API_VERSION change ->  complete breakage. No way to run older userspace on newer kernels.
new CAP ->  optional feature

If I read correctly you're changing quite a few existing interfaces, so old userspace wouldn't work anymore. Hence I'm proposing using activating the new way of dirty logging optionally.


The fact is, I am trying to keep the existing interfaces completely(KVM_API_VERSION part is my mistake).

For x86, I have checked that current qemu works without any change.
I mean we can use get_dirty_log() as is.

And as you propose, we can determine which api(swith_* or get_*) we use optionally.
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