On 22.11.21 16:09, Jason Gunthorpe wrote: > 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? Yes, I think we can phrase it that way, + "migrate provider" -- Thanks, David / dhildenb
