nitro_enclaves: Add logic for setting an enclave vCPU

nitro_enclaves: Add logic for setting an enclave vCPU

An enclave, before being started, has its resources set. One of its
resources is CPU.

A NE CPU pool is set and enclave CPUs are chosen from it. Offline the
CPUs from the NE CPU pool during the pool setup and online them back
during the NE CPU pool teardown. The CPU offline is necessary so that
there would not be more vCPUs than physical CPUs available to the
primary / parent VM. In that case the CPUs would be overcommitted and
would change the initial configuration of the primary / parent VM of
having dedicated vCPUs to physical CPUs.

The enclave CPUs need to be full cores and from the same NUMA node. CPU
0 and its siblings have to remain available to the primary / parent VM.

Add ioctl command logic for setting an enclave vCPU.

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

* Check for error return value when setting the kernel parameter string.
* 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.
* Calculate the number of threads per core and not use smp_num_siblings
  that is x86 specific.

v5 -> v6

* Check CPUs are from the same NUMA node before going through CPU
  siblings during the NE CPU pool setup.
* Update documentation to kernel-doc format.

v4 -> v5

* Set empty string in case of invalid NE CPU pool.
* Clear NE CPU pool mask on pool setup failure.
* Setup NE CPU cores out of the NE CPU pool.
* Early exit on NE CPU pool setup if enclave(s) already running.
* Remove sanity checks for situations that shouldn't happen, only if
  buggy system or broken logic at all.
* Add check for maximum vCPU id possible before looking into the CPU
  pool.
* Remove log on copy_from_user() / copy_to_user() failure and on admin
  capability check for setting the NE CPU pool.
* Update the ioctl call to not create a file descriptor for the vCPU.
* Split the CPU pool usage logic in 2 separate functions - one to get a
  CPU from the pool and the other to check the given CPU is available in
  the pool.

v3 -> v4

* Setup the NE CPU pool at runtime via a sysfs file for the kernel
  parameter.
* Check enclave CPUs to be from the same NUMA node.
* Use dev_err instead of custom NE log pattern.
* Update the NE ioctl call to match the decoupling from the KVM API.

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, ioctl and release.

v1 -> v2

* Add log pattern for NE.
* Update goto labels to match their purpose.
* Remove the BUG_ON calls.
* Check if enclave state is init when setting enclave vCPU.

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/20200921121732.44291-10-andraprs@amazon.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>