[PATCH v2] powerpc xmon: use `dcbf` inplace of `dcbi` instruction for 64bit Book3S

[Balamuruhan S <bala24@linux.ibm.com>]

Data Cache Block Invalidate (dcbi) instruction was implemented back in PowerPC
architecture version 2.03. It is obsolete and attempt to use of this illegal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>
---
 arch/powerpc/xmon/xmon.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)
---
changes in v2:
-------------
Fix review comments from Segher and Michael,
	* change incorrect architecture version 2.01 to 2.03 in commit
	  message.
	* ifdef it out the option `i` for PPC_BOOK3S_64 instead to drop it
	  and change the commit message accordingly.

diff --git a/arch/powerpc/xmon/xmon.c b/arch/powerpc/xmon/xmon.c
index 0ec9640335bb..bfd5a97689cd 100644
--- a/arch/powerpc/xmon/xmon.c
+++ b/arch/powerpc/xmon/xmon.c
@@ -335,10 +335,12 @@ static inline void cflush(void *p)
 	asm volatile ("dcbf 0,%0; icbi 0,%0" : : "r" (p));
 }
 
+#ifndef CONFIG_PPC_BOOK3S_64
 static inline void cinval(void *p)
 {
 	asm volatile ("dcbi 0,%0; icbi 0,%0" : : "r" (p));
 }
+#endif
 
 /**
  * write_ciabr() - write the CIABR SPR
@@ -1791,8 +1793,9 @@ static void prregs(struct pt_regs *fp)
 
 static void cacheflush(void)
 {
-	int cmd;
 	unsigned long nflush;
+#ifndef CONFIG_PPC_BOOK3S_64
+	int cmd;
 
 	cmd = inchar();
 	if (cmd != 'i')
@@ -1800,13 +1803,14 @@ static void cacheflush(void)
 	scanhex((void *)&adrs);
 	if (termch != '\n')
 		termch = 0;
+#endif
 	nflush = 1;
 	scanhex(&nflush);
 	nflush = (nflush + L1_CACHE_BYTES - 1) / L1_CACHE_BYTES;
 	if (setjmp(bus_error_jmp) == 0) {
 		catch_memory_errors = 1;
 		sync();
-
+#ifndef CONFIG_PPC_BOOK3S_64
 		if (cmd != 'i') {
 			for (; nflush > 0; --nflush, adrs += L1_CACHE_BYTES)
 				cflush((void *) adrs);
@@ -1814,6 +1818,10 @@ static void cacheflush(void)
 			for (; nflush > 0; --nflush, adrs += L1_CACHE_BYTES)
 				cinval((void *) adrs);
 		}
+#else
+		for (; nflush > 0; --nflush, adrs += L1_CACHE_BYTES)
+			cflush((void *)adrs);
+#endif
 		sync();
 		/* wait a little while to see if we get a machine check */
 		__delay(200);

base-commit: a87b93bdf800a4d7a42d95683624a4516e516b4f
-- 
2.24.1