powerpc/perf: Add support for SIER

On power8 we have a new SIER (Sampled Instruction Event Register), which
captures information about instructions when we have random sampling
enabled.

Add support for loading the SIER into pt_regs, overloading regs->dar.
Also set the new NO_SIPR flag in regs->result if we don't have SIPR.

Update regs_sihv/sipr() to look for SIPR/SIHV in SIER.

Signed-off-by: Michael Ellerman <michael@ellerman.id.au>
Acked-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>

arch/powerpc/include/asm/perf_event_server.h

@@ -53,6 +53,7 @@ struct power_pmu {
 #define PPMU_NO_CONT_SAMPLING	0x00000008 /* no continuous sampling */
 #define PPMU_SIAR_VALID		0x00000010 /* Processor has SIAR Valid bit */
 #define PPMU_HAS_SSLOT		0x00000020 /* Has sampled slot in MMCRA */
+#define PPMU_HAS_SIER		0x00000040 /* Has SIER */
 
 /*
  * Values for flags to get_alternatives()

arch/powerpc/include/asm/reg.h

@@ -671,6 +671,11 @@
 #define SPRN_PMC8	794
 #define SPRN_SIAR	780
 #define SPRN_SDAR	781
+#define SPRN_SIER	784
+#define   SIER_SIPR		0x2000000	/* Sampled MSR_PR */
+#define   SIER_SIHV		0x1000000	/* Sampled MSR_HV */
+#define   SIER_SIAR_VALID	0x0400000	/* SIAR contents valid */
+#define   SIER_SDAR_VALID	0x0200000	/* SDAR contents valid */
 
 #define SPRN_PA6T_MMCR0 795
 #define   PA6T_MMCR0_EN0	0x0000000000000001UL

arch/powerpc/perf/core-book3s.c

@@ -140,6 +140,9 @@ static bool regs_sihv(struct pt_regs *regs)
 {
 	unsigned long sihv = MMCRA_SIHV;
 
+	if (ppmu->flags & PPMU_HAS_SIER)
+		return !!(regs->dar & SIER_SIHV);
+
 	if (ppmu->flags & PPMU_ALT_SIPR)
 		sihv = POWER6_MMCRA_SIHV;
 
@@ -150,6 +153,9 @@ static bool regs_sipr(struct pt_regs *regs)
 {
 	unsigned long sipr = MMCRA_SIPR;
 
+	if (ppmu->flags & PPMU_HAS_SIER)
+		return !!(regs->dar & SIER_SIPR);
+
 	if (ppmu->flags & PPMU_ALT_SIPR)
 		sipr = POWER6_MMCRA_SIPR;
 
@@ -203,6 +209,7 @@ static inline u32 perf_get_misc_flags(struct pt_regs *regs)
 /*
  * Overload regs->dsisr to store MMCRA so we only need to read it once
  * on each interrupt.
+ * Overload regs->dar to store SIER if we have it.
  * Overload regs->result to specify whether we should use the MSR (result
  * is zero) or the SIAR (result is non zero).
  */
@@ -218,6 +225,18 @@ static inline void perf_read_regs(struct pt_regs *regs)
 	if (ppmu->flags & PPMU_NO_SIPR)
 		regs->result |= 2;
 
+	/*
+	 * On power8 if we're in random sampling mode, the SIER is updated.
+	 * If we're in continuous sampling mode, we don't have SIPR.
+	 */
+	if (ppmu->flags & PPMU_HAS_SIER) {
+		if (marked)
+			regs->dar = mfspr(SPRN_SIER);
+		else
+			regs->result |= 2;
+	}
+
+
 	/*
 	 * If this isn't a PMU exception (eg a software event) the SIAR is
 	 * not valid. Use pt_regs.