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    SubjectRe: [PATCH v3 0/5] x86: Show in sysfs if a memory node is able to do encryption
    On Tue, Dec 07, 2021 at 11:52:54AM -0800, Dave Hansen wrote:
    > On 12/7/21 11:45 AM, Martin Fernandez wrote:
    > >> I wonder, for example, why did you choose per-node reporting rather than
    > >> per-region as described in UEFI spec.
    > > Some time ago we discussed about this and concluded with Dave Hansen
    > > that it was better to do it in this per-node way.
    >
    > Physical memory regions aren't exposed to userspace in any meaningful way.

    Well, we have /sys/firmware/memory that exposes e820...

    > An ABI that says "everything is encrypted" is pretty meaningless and
    > only useful for this one, special case.
    >
    > A per-node ABI is useful for this case and is also useful going forward
    > if folks want to target allocations from applications to NUMA nodes
    > which have encryption capabilities. The ABI in this set is useful for
    > the immediate case and is useful to other folks.

    I don't mind per-node ABI, I'm just concerned that having a small region
    without the encryption flag set will render the entire node "not
    encryptable". This may happen because a bug in firmware, a user that shoot
    themself in a leg with weird memmap= or some hidden gem in interaction
    between e820, EFI and memblock that we still didn't discover.

    I agree that per-node flag is useful, but maybe we should also have better
    granularity as well.

    --
    Sincerely yours,
    Mike.

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