Re: [PATCH] Update virtio to latest ABI

Avi Kivity
2008-01-28T10:49:51Z

Anthony Liguori wrote:
>>
>> This ABI breakage is worrying. While it is expected to take some
>> time for the ABI to congeal, we need some way to prevent mismatched
>> guests and hosts from running. Perhaps something like the kvm abi
>> version, storedin the pci revision field? Keep incrementing it until
>> we are satisfied, then use feature bits to add functionality.
>
> This breakage wasn't actually necessary. We could have used a feature
> bit to indicate the additional net config field. In the very least,
> the additional net config field could have been added to the end of
> the config space so that old guests kept working that didn't use GSO.
>
> I don't think we need another mechanism to avoid breakages in the
> future. I think we have to declare that whatever ships in 2.6.25 is
> the stable ABI and make sure not to break it again in the future.

I'm worried about the ramp up to 2.6.25 causing confusion among users as
before that things will break left and right, if we don't provide a
tighter check.

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