nitro_enclaves: Add logic for terminating an enclave

nitro_enclaves: Add logic for terminating an enclave

An enclave is associated with an fd that is returned after the enclave
creation logic is completed. This enclave fd is further used to setup
enclave resources. Once the enclave needs to be terminated, the enclave
fd is closed.

Add logic for enclave termination, that is mapped to the enclave fd
release callback. Free the internal enclave info used for bookkeeping.

Changelog

v9 -> v10

* Update commit message to include the changelog before the SoB tag(s).

v8 -> v9

* Use the ne_devs data structure to get the refs for the NE PCI device.

v7 -> v8

* No changes.

v6 -> v7

* Remove the pci_dev_put() call as the NE misc device parent field is
  used now to get the NE PCI device.
* Update the naming and add more comments to make more clear the logic
  of handling full CPU cores and dedicating them to the enclave.

v5 -> v6

* Update documentation to kernel-doc format.
* Use directly put_page() instead of unpin_user_pages(), to match the
  get_user_pages() calls.

v4 -> v5

* Release the reference to the NE PCI device on enclave fd release.
* Adapt the logic to cpumask enclave vCPU ids and CPU cores.
* Remove sanity checks for situations that shouldn't happen, only if
  buggy system or broken logic at all.

v3 -> v4

* Use dev_err instead of custom NE log pattern.

v2 -> v3

* Remove the WARN_ON calls.
* Update static calls sanity checks.
* Update kzfree() calls to kfree().

v1 -> v2

* Add log pattern for NE.
* Remove the BUG_ON calls.
* Update goto labels to match their purpose.
* Add early exit in release() if there was a slot alloc error in the fd
  creation path.

Reviewed-by: Alexander Graf <graf@amazon.com>
Signed-off-by: Alexandru Vasile <lexnv@amazon.com>
Signed-off-by: Andra Paraschiv <andraprs@amazon.com>
Link: https://lore.kernel.org/r/20200921121732.44291-14-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>