On Fri, Aug 11, 2023 at 06:25:14PM +0200, David Hildenbrand wrote: > On 11.08.23 18:22, Peter Xu wrote: > > On Fri, Aug 11, 2023 at 06:17:05PM +0200, David Hildenbrand wrote: > > > We wouldn't touch "-mem-path". > > > > But still the same issue when someone uses -object memory-backend-file for > > hugetlb, mapping privately, expecting ram discard to work? > > > > Basically I see that example as, "hugetlb" in general made the private > > mapping over RW file usable, so forbidden that anywhere may take a risk. > > These users can be directed to using hugetlb > > a) using MAP_SHARED > b) using memory-backend-memfd, if MAP_PRIVATE is desired > > Am I missing any important use case? Are we being a bit to careful about > virtio-balloon and postcopy simply not being available for these corner > cases? The current immediate issue is not really mem=rw + fd=rw + private case (which was a known issue), but how to make mem=rw + fd=ro + private work for ThinnerBloger, iiuc. I'd just think it safer to expose that cap to solve problem A (vm templating) without affecting problem B (fallcate-over-private not working right), when B is uncertain. I'm also copy Daniel & libvirt list in case there's quick comment from there. Say, maybe libvirt never use private mapping on hugetlb files over memory-backend-file at all, then it's probably fine. In all cases, you and Igor should have the final grasp; no stand on a strong opinon from my side. -- Peter Xu
