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    SubjectRe: [PATCH v2 14/18] x86/sgx: Add EPC OOM path to forcefully reclaim EPC
    On Mon, Dec 12, 2022 at 06:09:39PM +0000, Sean Christopherson wrote:
    > On Fri, Dec 09, 2022, Dave Hansen wrote:
    > > On 12/9/22 08:05, Kristen Carlson Accardi wrote:
    > > > Aside from that though, I don't think that killing enclaves makes sense
    > > > outside the context of cgroup limits.
    > >
    > > I think it makes a lot of sense in theory. Whatever situation we get
    > > into with a cgroup's EPC we can also get into with the whole system's EPC.
    > >
    > > *But*, it's orders of magnitude harder to hit on the whole system.
    >
    > ...
    >
    > > If someone wants to extend this OOM support to system-wide EPC later, then go
    > > ahead. But, I don't think it makes a lot of sense to invert this series for
    > > it.
    >
    > +1 from the peanut gallery. With VMM EPC oversubscription suport, no sane VMM
    > will oversubscribe VEPC pages. And for VA pages, supporting swap of VA pages is
    > likely a more userspace-friendly approach if system-wide EPC OOM is a concern.

    When swapping VA pages the topology of the VA page cache for swapped VA
    pages is the main question. It is compromise between how long swap-in and
    swap-out can take, and how generic solution it be, meaning how deep
    hierarchies you want to build, or is just a flat list of parent VA pages
    "good enough".

    Also, there's the question whether it should be a global cache, per cgroup
    and so forth.

    Implementing any solution is not overly complicated. Locking in these
    options is what puzzles me.

    BR, Jarkko

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