[PATCH 5/5] powerpc/perf: use regs->nip when siar is zero

[Madhavan Srinivasan]

In power10 DD1, there is an issue where the
Sampled Instruction Address Register (SIAR)
not latching to the sampled address during
random sampling. This results in value of 0s
in the SIAR. Patch adds a check to use regs->nip
when SIAR is zero.

Signed-off-by: Madhavan Srinivasan <maddy at linux.ibm.com>
---
 arch/powerpc/perf/core-book3s.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index e675c7c8ce0e..63de77eb0ac0 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -263,9 +263,16 @@ static inline u32 perf_get_misc_flags(struct pt_regs *regs)
 	 * DD1.
 	 */
 	if (marked && (ppmu->flags & PPMU_P10_DD1)) {
-		if (is_kernel_addr(mfspr(SPRN_SIAR)))
-			return PERF_RECORD_MISC_KERNEL;
-		return PERF_RECORD_MISC_USER;
+		unsigned long siar = mfspr(SPRN_SIAR);
+		if (siar) {
+			if (is_kernel_addr(siar))
+				return PERF_RECORD_MISC_KERNEL;
+			return PERF_RECORD_MISC_USER;
+		} else {
+			if (is_kernel_addr(regs->nip))
+				return PERF_RECORD_MISC_KERNEL;
+			return PERF_RECORD_MISC_USER;
+		}
 	}
 
 	/*
@@ -2211,8 +2218,14 @@ unsigned long perf_misc_flags(struct pt_regs *regs)
 unsigned long perf_instruction_pointer(struct pt_regs *regs)
 {
 	bool use_siar = regs_use_siar(regs);
+	unsigned long siar = mfspr(SPRN_SIAR);
 
-	if (use_siar && siar_valid(regs))
+	if (ppmu->flags & PPMU_P10_DD1) {
+		if (siar)
+			return siar;
+		else
+			return regs->nip;
+	} else if (use_siar && siar_valid(regs))
 		return mfspr(SPRN_SIAR) + perf_ip_adjust(regs);
 	else if (use_siar)
 		return 0;		// no valid instruction pointer
-- 
2.26.2