On 5/2/23 11:19 AM, Lorenzo Stoakes wrote: > 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? > Sure, will do!
