Hi Dan, Laszlo, On 06/14/2018 10:59 AM, Daniel P. Berrangé wrote: > On Thu, Jun 14, 2018 at 10:56:20AM +0200, Laszlo Ersek wrote: >> Hi Eric, >> >> On 06/14/18 08:27, Auger Eric wrote: >>> Hi Laszlo, >>> >>> On 06/13/2018 11:05 PM, Laszlo Ersek wrote: >>>> On 06/13/18 10:48, Eric Auger wrote: >>>> >>>>> PATCH: merge of ECAM and VCPU extension >>>>> - Laszlo reviewed the ECAM changes but I dropped his R-b >>>>> due to the squash >>>> >>>> Was there any particular reason why the previous patch set (with only >>>> the ECAM enlargement) couldn't be merged first? To be honest I'm not >>>> super happy when my R-b is dropped for non-technical reasons; it seems >>>> like wasted work for both of us. >>>> >>>> Obviously if there's a technical dependency or some other reason why >>>> committing the ECAM enlargement in separation would be *wrong*, that's >>>> different. Even in that case, wouldn't it be possible to keep the >>>> initial virt-3.0 machtype addition as I reviewed it, and then add the >>>> rest in an incremental patch? >>> >>> Sorry about that. My fear was about migration. We would have had 2 virt >>> 3.0 machine models not supporting the same features. While bisecting >>> migration we could have had the source using the high mem ECAM and the >>> destination not supporting it. So I preferred to avoid this trouble by >>> merging the 2 features in one patch. However I may have kept your R-b >>> restricting its scope to the ECAM stuff. >> >> to my understanding, it is normal to *gradually* add new properties >> during the development cycle, to the new machine type of the upcoming >> QEMU release. To my understanding, it's not expected that migration work >> between development snapshots built from git. What matters is that two >> official releases, specifying the same machine type, enable the user to >> migrate a guest between them (in forward direction). >> >> In every release, so many new features are introduced that it's >> impossible to introduce the new machine type with all the compat knobs >> added at once. Instead, the new machine type is introduced when the >> first feature that requires a compat knob is added to git. All other >> such features extend the compat knobs gradually, during the development >> cycle. Until the new official release is made (which contains all the >> compat knobs for all the new features), the new machine type simply >> doesn't exist, as far as the public is concerned, so it cannot partake >> in migration either. >> >> This is my understanding anyway. > > That is correct - there is ZERO expectation of migration / ABI stability > between arbitrary GIT snapshots, only official releases. Prior to the > first release including it, a versioned machine type can be changed > arbitrarily. OK so sufficient consensus on this then.
Thanks Eric > > Regards, > Daniel >
