[PATCH v5 16/21] powerpc: Enable Prefixed Instructions

[Jordan Niethe]

From: Alistair Popple <alistair at popple.id.au>

Prefix instructions have their own FSCR bit which needs to enabled via
a CPU feature. The kernel will save the FSCR for problem state but it
needs to be enabled initially.

If prefixed instructions are made unavailable by the [H]FSCR, attempting
to use them will cause a facility unavailable exception. Add "PREFIX" to
the facility_strings[].

Currently there are no prefixed instructions that are actually emulated
by emulate_instruction() within facility_unavailable_exception().
However, when caused by a prefixed instructions the SRR1 PREFIXED bit is
set. Prepare for dealing with emulated prefixed instructions by checking
for this bit.

Reviewed-by: Nicholas Piggin <npiggin at gmail.com>
Signed-off-by: Alistair Popple <alistair at popple.id.au>
Signed-off-by: Jordan Niethe <jniethe5 at gmail.com>
---
v4:
    - Squash "Check for prefixed instructions in
      facility_unavailable_exception()" here
    - Remove dt parts for now
---
 arch/powerpc/include/asm/reg.h | 3 +++
 arch/powerpc/kernel/traps.c    | 1 +
 2 files changed, 4 insertions(+)

diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index 1aa46dff0957..c7758c2ccc5f 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -397,6 +397,7 @@
 #define SPRN_RWMR	0x375	/* Region-Weighting Mode Register */
 
 /* HFSCR and FSCR bit numbers are the same */
+#define FSCR_PREFIX_LG	13	/* Enable Prefix Instructions */
 #define FSCR_SCV_LG	12	/* Enable System Call Vectored */
 #define FSCR_MSGP_LG	10	/* Enable MSGP */
 #define FSCR_TAR_LG	8	/* Enable Target Address Register */
@@ -408,11 +409,13 @@
 #define FSCR_VECVSX_LG	1	/* Enable VMX/VSX  */
 #define FSCR_FP_LG	0	/* Enable Floating Point */
 #define SPRN_FSCR	0x099	/* Facility Status & Control Register */
+#define   FSCR_PREFIX	__MASK(FSCR_PREFIX_LG)
 #define   FSCR_SCV	__MASK(FSCR_SCV_LG)
 #define   FSCR_TAR	__MASK(FSCR_TAR_LG)
 #define   FSCR_EBB	__MASK(FSCR_EBB_LG)
 #define   FSCR_DSCR	__MASK(FSCR_DSCR_LG)
 #define SPRN_HFSCR	0xbe	/* HV=1 Facility Status & Control Register */
+#define   HFSCR_PREFIX	__MASK(FSCR_PREFIX_LG)
 #define   HFSCR_MSGP	__MASK(FSCR_MSGP_LG)
 #define   HFSCR_TAR	__MASK(FSCR_TAR_LG)
 #define   HFSCR_EBB	__MASK(FSCR_EBB_LG)
diff --git a/arch/powerpc/kernel/traps.c b/arch/powerpc/kernel/traps.c
index 82a3438300fd..a4764b039749 100644
--- a/arch/powerpc/kernel/traps.c
+++ b/arch/powerpc/kernel/traps.c
@@ -1720,6 +1720,7 @@ void facility_unavailable_exception(struct pt_regs *regs)
 		[FSCR_TAR_LG] = "TAR",
 		[FSCR_MSGP_LG] = "MSGP",
 		[FSCR_SCV_LG] = "SCV",
+		[FSCR_PREFIX_LG] = "PREFIX",
 	};
 	char *facility = "unknown";
 	u64 value;
-- 
2.17.1