On Mon, Nov 22, 2021 at 03:57:17PM +0100, David Hildenbrand wrote: > 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 ). Sounds like it is a swap provider more than an owner? Jason
