On 22.04.2021 17:28, Juergen Gross wrote: > On 22.04.21 17:23, Jan Beulich wrote: >> On 22.04.2021 17:17, Juergen Gross wrote: >>> On 22.04.21 17:16, Jan Beulich wrote: >>>> On 22.04.2021 17:10, Juergen Gross wrote: >>>>> Some features of Xen can be assumed to be always present, so add a >>>>> central check to verify this being true and remove the other checks. >>>>> >>>>> Juergen Gross (3): >>>>> xen: check required Xen features >>>>> xen: assume XENFEAT_mmu_pt_update_preserve_ad being set for pv guests >>>>> xen: assume XENFEAT_gnttab_map_avail_bits being set for pv guests >>>> >>>> I wonder whether it's a good idea to infer feature presence from >>>> version numbers. If (at some point in the past) you had inferred >>>> gnttab v2 being available by version, this would have been broken >>>> by its availability becoming controllable by a command line option >>>> in Xen. >>> >>> I'm testing the feature to be really present when booting and issue a >>> message if it is not there. >> >> And how does this help if the feature really isn't there yet other code >> assumes it is? > > Did you look at the features I'm testing?
I did, yes. > Those are really just low > level additions I can't imagine will ever be removed again. I don't expect them to be removed. But I don't think the people having contributed gnttab v2 expected any such for it, either. Jan
