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    SubjectRe: [PATCH v10 02/14] KVM: Cache as_id in kvm_memory_slot
    On Tue, Jul 07, 2020 at 03:50:09PM -0400, Peter Xu wrote:
    > On Mon, Jul 06, 2020 at 11:17:32PM -0700, Sean Christopherson wrote:
    > > On Fri, Jul 03, 2020 at 02:41:22PM -0400, Peter Xu wrote:
    > > > On Thu, Jul 02, 2020 at 04:08:49PM -0700, Sean Christopherson wrote:
    > > > > This technically needs to set as_id in the deleted memslot. I highly doubt
    > > > > it will ever matter from a functionality perspective, but it'd be confusing
    > > > > to encounter a memslot whose as_id did not match that of its owner.
    > > >
    > > > Yeah it shouldn't matter because as_id is directly passed in to look up the
    > > > pointer of kvm_memslots in kvm_delete_memslot, and memslot->as_id shouldn't be
    > > > further referenced.
    > > >
    > > > I can add a comment above if this can clarify things a bit:
    > > >
    > > > + u16 as_id; /* cache of as_id; only valid if npages != 0 */
    > >
    > > Why not just set it?
    >
    > Because the value is useless even if set? :)

    It's useless when things go according to plan, but I can see it being useful
    if there's a bug that leads to consumption of a deleted memslot. Maybe not
    "useful" so much as "not misleading".

    > You mean in kvm_delete_memslot(), am I right?

    Yes.

    > > It's a single line of code, and there's more than one
    > > "shouldn't" in the above.
    >
    > If you want, I can both set it and add the comment. Thanks,

    Why bother with the comment? It'd be wrong in the sense that the as_id is
    always valid/accurate, even if npages == 0.

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