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powerpc/perf: Fix the check for SIAR value

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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: 2ca13a4cc5 ("powerpc/perf: Use regs->nip when SIAR is zero")
Signed-off-by: Kajol Jain <kjain@linux.ibm.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://lore.kernel.org/r/20210818171556.36912-3-kjain@linux.ibm.com
This commit is contained in:
Kajol Jain 2021-08-18 22:45:56 +05:30 • committed by Michael Ellerman
parent cc90c6742e
commit 3c69a5f222
1 changed files with 1 additions and 7 deletions
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8
arch/powerpc/perf/core-book3s.c
View file

@ -2260,15 +2260,9 @@ 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;