Re: [RFC] KVM: mm: fd-based approach for supporting KVM guest private memory

[Andy Lutomirski]

On 9/3/21 12:14 PM, Kirill A. Shutemov wrote:
> On Thu, Sep 02, 2021 at 08:33:31PM +0000, Sean Christopherson wrote:
>> Would requiring the size to be '0' at F_SEAL_GUEST time solve that problem?
> 
> I guess. Maybe we would need a WRITE_ONCE() on set. I donno. I will look
> closer into locking next.

We can decisively eliminate this sort of failure by making the switch
happen at open time instead of after.  For a memfd-like API, this would
be straightforward.  For a filesystem, it would take a bit more thought.