KVM: guest_memfd: Split bind() into prepare()+commit() phases

Split binding a memslot to a guest_memfd instance into prepare() and
commit() phases so that KVM can separate preparing the memslot from binding
the memslot to the gmem instance, i.e. from committing the memslot.  This
will allow waiting to commit the memslot+gmem binding until the memslot is
fully prepared, which is necessary as the memslot becomes reachable when
the binding is created.

As a bonus, drop the unwind-on-failure from the commit phase (other than
nullifying the bindings), as the only reason bind() did the full unwind is
because it technically didn't own the memslot, i.e. "needed" to leave
memslot in the same state it started in.

No functional change intended (the unwinding down on bind() failure was
effectively dead code since KVM simply deletes the memslot on failure,
i.e. there was nothing that could actually observe the unwind).

Cc: stable@vger.kernel.org
Reviewed-by: David Hildenbrand (Arm) <david@kernel.org>
Link: https://patch.msgid.link/20260922001332.1121266-5-seanjc@google.com
Signed-off-by: Sean Christopherson <seanjc@google.com>

0 files changed, 0 insertions, 0 deletions