[PATCH v4 3/3] powerpc/perf: Fix the check for SIAR value

[Kajol Jain]

Incase of random sampling, there can be scenarios where
Sample Instruction Address Register(SIAR) may not latch
to the sampled instruction and could result in
the value of 0. In these scenarios it is preferred to
return regs->nip. These corner cases are seen in the
previous generation (p9) also.

Patch adds the check for SIAR value along with regs_use_siar
and siar_valid checks so that the function will return
regs->nip incase SIAR is zero.

Patch drops the code under PPMU_P10_DD1 flag check
which handles SIAR 0 case only for Power10 DD1.

Fixes: 2ca13a4cc56c9 ("powerpc/perf: Use regs->nip when SIAR is zero")
Signed-off-by: Kajol Jain <kjain at linux.ibm.com>
---

Changelog:
v3 -> v4
- Remove use_siar variable and directly using regs_use_siar call as
  suggested by Christophe Leroy

v2 -> v3
- Drop adding new ternary condition to check siar value.
- Remove siar check specific for PPMU_P10_DD1 and add
  it along with common checks as suggested by Christophe Leroy
  and Michael Ellermen

 arch/powerpc/perf/core-book3s.c | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 23ec89a59893..b0a589409039 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -2251,15 +2251,9 @@ 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 (ppmu && (ppmu->flags & PPMU_P10_DD1)) {
-		if (siar)
-			return siar;
-		else
-			return regs->nip;
-	} else if (use_siar && siar_valid(regs))
+	if (regs_use_siar(regs) && siar_valid(regs) && siar)
 		return siar + perf_ip_adjust(regs);
 	else
 		return regs->nip;
-- 
2.26.2