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. > > Which, again, makes it weird/wrong that this KVM code is pinning it > again :\ > > Jason
