powerpc/lib/sstep: fix 'ptesync' build error

stable inclusion
from stable-v5.10.102
commit fb26219b40467e32b57221b9dfd245c2f7de95f7
bugzilla: https://gitee.com/openeuler/kernel/issues/I567K6

Reference: https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fb26219b40467e32b57221b9dfd245c2f7de95f7

--------------------------------

commit fe663df7 upstream.

Building tinyconfig with gcc (Debian 11.2.0-16) and assembler (Debian
2.37.90.20220207) the following build error shows up:

  {standard input}: Assembler messages:
  {standard input}:2088: Error: unrecognized opcode: `ptesync'
  make[3]: *** [/builds/linux/scripts/Makefile.build:287: arch/powerpc/lib/sstep.o] Error 1

Add the 'ifdef CONFIG_PPC64' around the 'ptesync' in function
'emulate_update_regs()' to like it is in 'analyse_instr()'. Since it looks like
it got dropped inadvertently by commit 3cdfcbfd ("powerpc: Change
analyse_instr so it doesn't modify *regs").

A key detail is that analyse_instr() will never recognise lwsync or
ptesync on 32-bit (because of the existing ifdef), and as a result
emulate_update_regs() should never be called with an op specifying
either of those on 32-bit. So removing them from emulate_update_regs()
should be a nop in terms of runtime behaviour.

Fixes: 3cdfcbfd ("powerpc: Change analyse_instr so it doesn't modify *regs")
Cc: stable@vger.kernel.org # v4.14+
Suggested-by: NArnd Bergmann <arnd@arndb.de>
Signed-off-by: NAnders Roxell <anders.roxell@linaro.org>
[mpe: Add last paragraph of change log mentioning analyse_instr() details]
Signed-off-by: NMichael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20220211005113.1361436-1-anders.roxell@linaro.orgSigned-off-by: NGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: NYu Liao <liaoyu15@huawei.com>
Reviewed-by: NWei Li <liwei391@huawei.com>
Signed-off-by: NZheng Zengkai <zhengzengkai@huawei.com>

arch/powerpc/lib/sstep.c

@@ -3062,12 +3062,14 @@ void emulate_update_regs(struct pt_regs *regs, struct instruction_op *op)
 		case BARRIER_EIEIO:
 			eieio();
 			break;
+#ifdef CONFIG_PPC64
 		case BARRIER_LWSYNC:
 			asm volatile("lwsync" : : : "memory");
 			break;
 		case BARRIER_PTESYNC:
 			asm volatile("ptesync" : : : "memory");
 			break;
+#endif
 		}
 		break;