powerpc/xmon: don't access ASDR in VMs

powerpc/xmon: don't access ASDR in VMs

commit c2a20711fc181e7f22ee5c16c28cb9578af84729 upstream.

ASDR is HV-privileged and must only be accessed in HV-mode.
Fixes a Program Check (0x700) when xmon in a VM dumps SPRs.

Fixes: d1e1b351f50f ("powerpc/xmon: Add ISA v3.0 SPRs to SPR dump")
Cc: stable@vger.kernel.org # v4.14+
Signed-off-by: Sukadev Bhattiprolu <sukadev@linux.ibm.com>
Reviewed-by: Andrew Donnellan <ajd@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200107021633.GB29843@us.ibm.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>