nitro_enclaves: Add logic for starting an enclave

After all the enclave resources are set, the enclave is ready for
beginning to run.

Add ioctl command logic for starting an enclave after all its resources,
memory regions and CPUs, have been set.

The enclave start information includes the local channel addressing -
vsock CID - and the flags associated with the enclave.

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

* Add check for invalid enclave CID value e.g. well-known CIDs and
  parent VM CID.
* Add custom error code for incorrect flag in enclave start info and
  invalid enclave CID.

v6 -> v7

* 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

* Check for invalid enclave start flags.
* Update documentation to kernel-doc format.

v4 -> v5

* Add early exit on enclave start ioctl function call error.
* Move sanity checks in the enclave start ioctl function, outside of the
  switch-case block.
* Remove log on copy_from_user() / copy_to_user() failure.

v3 -> v4

* Use dev_err instead of custom NE log pattern.
* Update the naming for the ioctl command from metadata to info.
* Check for minimum enclave memory size.

v2 -> v3

* Remove the WARN_ON calls.
* Update static calls sanity checks.

v1 -> v2

* Add log pattern for NE.
* Check if enclave state is init when starting an enclave.
* Remove the BUG_ON calls.

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/20200921121732.44291-13-andraprs@amazon.com


Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>