arm64: add HCRX_EL2 register

[harry.moulton_arm.com]

Summary

HCRX_EL2 is the Extended Hypervisor Configuration Register introduced
with FEAT_HCX in ARMv8.7. All fields in this register are used for
features in ARMv8.7 and above. Initially zero the register, incase
firmware has not properly configured it.

Sponsored By: Arm Ltd
Signed-off-by: Harry Moulton <[e-mail]>

[andrew]

sys/arm64/arm64/locore.S

378–390

Is there a reason to put this in a VHE only code path? It's also unlikely to need the isb as there is one before the eret that can be used as the context synchronization event.

sys/arm64/include/armreg.h

721–727 ↗

(On Diff #149676)

This should be in hypervisor.h as it's an EL2 only register.

[harry.moulton_arm.com]

Moved HCRX register definition to hypervisor.h, moved initial
configuration of hcrx_el2 to after .Ldone_vhe

[andrew]

sys/arm64/arm64/locore.S

400

This will trash the cptr_el2 value. After msr spsr_el2, x5 will be safe as that's the last register set based on VHE vs non-VHE/

[harry.moulton_arm.com]

Move configuration of hcrx_el2 to avoid trashing cptr_el2