Data Cache Block Invalidate (dcbi) instruction implemented back in
PowerPC architecture version 2.03. But as per Power Processor Users Manual
it is obsolete and not supported by POWER8/POWER9 core. Attempt to use of
this illegal instruction results in a hypervisor emulation assistance
interrupt. So, ifdef it out the option `i` in xmon for 64bit Book3S.

  0:mon> fi
  cpu 0x0: Vector: 700 (Program Check) at [c000000003be74a0]
      pc: c000000000102030: cacheflush+0x180/0x1a0
      lr: c000000000101f3c: cacheflush+0x8c/0x1a0
      sp: c000000003be7730
     msr: 8000000000081033
    current = 0xc0000000035e5c00
    paca    = 0xc000000001910000   irqmask: 0x03   irq_happened: 0x01
      pid   = 1025, comm = bash
  Linux version 5.6.0-rc5-g5aa19adac (root@ltc-wspoon6) (gcc version 7.4.0
  (Ubuntu 7.4.0-1ubuntu1~18.04.1)) #1 SMP Tue Mar 10 04:38:41 CDT 2020
  cpu 0x0: Exception 700 (Program Check) in xmon, returning to main loop
  [c000000003be7c50] c00000000084abb0 __handle_sysrq+0xf0/0x2a0
  [c000000003be7d00] c00000000084b3c0 write_sysrq_trigger+0xb0/0xe0
  [c000000003be7d30] c0000000004d1edc proc_reg_write+0x8c/0x130
  [c000000003be7d60] c00000000040dc7c __vfs_write+0x3c/0x70
  [c000000003be7d80] c000000000410e70 vfs_write+0xd0/0x210
  [c000000003be7dd0] c00000000041126c ksys_write+0xdc/0x130
  [c000000003be7e20] c00000000000b9d0 system_call+0x5c/0x68
  --- Exception: c01 (System Call) at 00007fffa345e420
  SP (7ffff0b08ab0) is in userspace
Signed-off-by: Balamuruhan S <bala24@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20200330075954.538773-1-bala24@linux.ibm.com