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    SubjectRe: [RFC v2 PATCH 01/13] mm/shmem: Introduce F_SEAL_GUEST
    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?

    "no new access" makes sense to me, we have access through
    read/write/mmap/splice/etc and access to pages through the private in
    kernel interface (kvm, iommu)

    Jason

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