nitro_enclaves: Add logic for creating an enclave VM

nitro_enclaves: Add logic for creating an enclave VM

Add ioctl command logic for enclave VM creation. It triggers a slot
allocation. The enclave resources will be associated with this slot and
it will be used as an identifier for triggering enclave run.

Return a file descriptor, namely enclave fd. This is further used by the
associated user space enclave process to set enclave resources and
trigger enclave termination.

The poll function is implemented in order to notify the enclave process
when an enclave exits without a specific enclave termination command
trigger e.g. when an enclave crashes.

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

* Use the NE misc device parent field 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 the code base to init the ioctl function in this patch.
* Update documentation to kernel-doc format.

v4 -> v5

* Release the reference to the NE PCI device on create VM error.
* Close enclave fd on copy_to_user() failure; rename fd to enclave fd
  while at it.
* Remove sanity checks for situations that shouldn't happen, only if
  buggy system or broken logic at all.
* Remove log on copy_to_user() failure.

v3 -> v4

* Use dev_err instead of custom NE log pattern.
* Update the NE ioctl call to match the decoupling from the KVM API.
* Add metadata for the NUMA node for the enclave memory and CPUs.

v2 -> v3

* Remove the WARN_ON calls.
* Update static calls sanity checks.
* Update kzfree() calls to kfree().
* Remove file ops that do nothing for now - open.

v1 -> v2

* Add log pattern for NE.
* Update goto labels to match their purpose.
* 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/20200921121732.44291-9-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>