On Tue, May 02, 2023 at 05:09:06PM +0200, David Hildenbrand wrote: > On 02.05.23 15:56, Matthew Rosato wrote: > > On 5/2/23 9:50 AM, Jason Gunthorpe wrote: > > > On Tue, May 02, 2023 at 03:47:43PM +0200, David Hildenbrand wrote: > > > > > Eventually we want to implement a mechanism where we can dynamically pin in response to RPCIT. > > > > > > > > Okay, so IIRC we'll fail starting the domain early, that's good. And if we > > > > pin all guest memory (instead of small pieces dynamically), there is little > > > > existing use for file-backed RAM in such zPCI configurations (because memory > > > > cannot be reclaimed either way if it's all pinned), so likely there are no > > > > real existing users. > > > > > > Right, this is VFIO, the physical HW can't tolerate not having pinned > > > memory, so something somewhere is always pinning it. > > > > I might have mis-explained above. > > > > With iommufd nesting, we will pin everything upfront as a starting point. > > > > The current usage of vfio type1 iommu for s390 does not pin the entirety of guest memory upfront, it happens as guest RPCITs occur / type1 mappings are made. > > ... so, after the domain started successfully on the libvirt/QEMU side ? :/ > > It would be great to confirm that. There might be a BUG in patch #2 (see my > reply to patch #2) that might not allow you to reproduce it right now. > Yes apologies - thank you VERY much for doing this Matthew, but apologies, I made rather a clanger in patch 2 which would mean fast patch degrading to slow path would pass even for file-backed. Will respin a v7 + cc you on that, if you could be so kind as to test that? > -- > Thanks, > > David / dhildenb >
