KVM: x86: Untag addresses for LAM emulation where applicable

Stub in vmx_get_untagged_addr() and wire up calls from the emulator (via
get_untagged_addr()) and "direct" calls from various VM-Exit handlers in
VMX where LAM untagging is supposed to be applied.  Defer implementing
the guts of vmx_get_untagged_addr() to future patches purely to make the
changes easier to consume.

LAM is active only for 64-bit linear addresses and several types of
accesses are exempted.

- Cases need to untag address (handled in get_vmx_mem_address())
  Operand(s) of VMX instructions and INVPCID.
  Operand(s) of SGX ENCLS.

- Cases LAM doesn't apply to (no change needed)
  Operand of INVLPG.
  Linear address in INVPCID descriptor.
  Linear address in INVVPID descriptor.
  BASEADDR specified in SECS of ECREATE.

Note:
  - LAM doesn't apply to write to control registers or MSRs
  - LAM masking is applied before walking page tables, i.e. the faulting
    linear address in CR2 doesn't contain the metadata.
  - The guest linear address saved in VMCS doesn't contain metadata.

Signed-off-by: Binbin Wu <binbin.wu@linux.intel.com>
Reviewed-by: Chao Gao <chao.gao@intel.com>
Tested-by: Xuelian Guo <xuelian.guo@intel.com>
Link: https://lore.kernel.org/r/20230913124227.12574-10-binbin.wu@linux.intel.com


[sean: massage changelog]
Signed-off-by: Sean Christopherson <seanjc@google.com>