On 22.11.21 15:01, Jason Gunthorpe wrote: > On Mon, Nov 22, 2021 at 02:35:49PM +0100, David Hildenbrand wrote: >> On 22.11.21 14:31, Jason Gunthorpe wrote: >>> On Mon, Nov 22, 2021 at 10:26:12AM +0100, David Hildenbrand wrote: >>> >>>> I do wonder if we want to support sharing such memfds between processes >>>> in all cases ... we most certainly don't want to be able to share >>>> encrypted memory between VMs (I heard that the kernel has to forbid >>>> that). It would make sense in the use case you describe, though. >>> >>> If there is a F_SEAL_XX that blocks every kind of new access, who >>> cares if userspace passes the FD around or not? >> I was imagining that you actually would want to do some kind of "change >> ownership". But yeah, the intended semantics and all use cases we have >> in mind are not fully clear to me yet. If it's really "no new access" >> (side note: is "access" the right word?) then sure, we can pass the fd >> around. > > What is "ownership" in a world with kvm and iommu are reading pages > out of the same fd? In the world of encrypted memory / TDX, KVM somewhat "owns" that memory IMHO (for example, only it can migrate or swap out these pages; it's might be debatable if the TDX module or KVM actually "own" these pages ). -- Thanks, David / dhildenb
