On 18/05/2022 11:30, Luca Fancellu wrote: >> On 18 May 2022, at 11:12, Andrew Cooper <andrew.coop...@citrix.com> wrote: >> >> On 18/05/2022 10:51, Edwin Torok wrote: >>>> diff --git a/tools/ocaml/libs/xc/xenctrl.ml >>>> b/tools/ocaml/libs/xc/xenctrl.ml >>>> index 7503031d8f61..8eab6f60eb14 100644 >>>> --- a/tools/ocaml/libs/xc/xenctrl.ml >>>> +++ b/tools/ocaml/libs/xc/xenctrl.ml >>>> @@ -85,6 +85,7 @@ type domctl_create_config = >>>> max_grant_frames: int; >>>> max_maptrack_frames: int; >>>> max_grant_version: int; >>>> + cpupool_id: int32; >>> What are the valid values for a CPU pool id, in particular what value >>> should be passed here to get back the behaviour prior to these changes in >>> Xen? >>> (i.e. would it be cpu pool id 0 or -1 if cpu pools aren't otherwise >>> explicitly configured on the system) >> cpupools are a non-optional construct in Xen. >> >> By default, one cpupool exists, with the id 0, using the default >> scheduler covering all pCPUs, and dom0 is constructed in this cpupool. >> >> Passing 0 here is the backwards compatible option. >> >> And on that note, Luca, you ought to patch xl/libxl to apply the pool= >> setting directly during domain create, rather than depending on cpupool >> 0 existing and moving the domain later. > Is it an enhancement or a bug fix?
This isn't a binary option. Your series added an optimisation to DOMCTL_createdomain, then didn't adjust libxl to use the optimisation (which would have reduced the number of hypercalls to create the domain, and reduce the number of dynamic memory allocations in the hypervisor. Marginal, certainly, but clearly a nice-to-have). Therefore, you created technical debt, which is option 3. By default, as the contributor, you are expected to address the technical debt, because it is an important difference between hacking a feature up for yourself, and integrating the feature nicely for everyone. You can of course negotiate with the tools maintainer to see if they care, and right now that's a bit difficult. It's quite possible that noone other than me cares, and I'm not libxl maintainer. Either you need to pay off the technical debt, or someone else will have to. Someone else is going to have to start with digging into source history, which means it's more expensive than you doing it now. At an absolute minimum, you need to be aware of where/when you are creating technical debt. > From what I know, please correct me if I’m wrong, cpupool0 > Is always present, so there won’t be problem on assuming its existence From what I can see, your series has reduced the magic involved with cpupool0, which is good. But the fact that it still has magic properties is still technical debt that someone is going to have to pay off eventually. ~Andrew
