x86/hvm: Correct the emulated interaction of invlpg with segments

x86/hvm: Correct the emulated interaction of invlpg with segments

The `invlpg` instruction is documented to take a memory address, and is not
documented to suffer faults from segmentation violations.  It is also
explicitly documented to be a NOP when issued on a non-canonical address.

Experimentally, and subsequently confirmed by both Intel and AMD, the
instruction does take into account segment bases, but will happily invalidate
a TLB entry for a mapping beyond the segment limit.

The emulation logic will currently raise #GP/#SS faults for segment limit
violations, or non-canonical addresses, which doesn't match hardware's
behaviour.  Instead, squash exceptions generated by
hvmemul_virtual_to_linear() and proceed with invalidation.

Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Paul Durrant <paul.durrant@citrix.com>
Release-acked-by: Wei Liu <wei.liu2@citrix.com>