[PATCH v3] powerpc/perf: Set cpumode flags using sample address
Anjali K
anjalik at linux.ibm.com
Tue May 28 14:03:56 AEST 2024
Currently in some cases, when the sampled instruction address register
latches to a specific address during sampling, the privilege bits captured
in the sampled event register are incorrect.
For example, a snippet from the perf report on a power10 system is:
Overhead Address Command Shared Object Symbol
........ .................. ............ ................. .......................
2.41% 0x7fff9f94a02c null_syscall [unknown] [k] 0x00007fff9f94a02c
2.20% 0x7fff9f94a02c null_syscall libc.so.6 [.] syscall
perf_get_misc_flags() function looks at the privilege bits to return the
corresponding flags to be used for the address symbol and these privilege
bit details are read from the sampled event register. In the above snippet,
address "0x00007fff9f94a02c" is shown as "k" (kernel) due to the incorrect
privilege bits captured in the sampled event register.
To address this case check whether the sampled address is in the kernel
area. Since this is specific to the latest platform, a new pmu flag is
added called "PPMU_P10" and is used to contain the proposed fix.
PPMU_P10_DD1 marked events are also included under PPMU_P10, hence
remove the code specific to PPMU_P10_DD1 marked events.
Signed-off-by: Anjali K <anjalik at linux.ibm.com>
---
Changelog:
v2->v3:
Addressed review comments from Michael Ellerman to change the commit
message and update the values of PPMU_P10 and PPMU_HAS_ATTR_CONFIG1 flags
to move the PPMU_P10 flag near the PPMU_P10_DD1 flag
Rebased on linux 6.10-rc1
v2 patch link:
https://lore.kernel.org/linuxppc-dev/20240517094607.422166-1-anjalik@linux.ibm.com/
v1->v2:
Fixed the build warning reported by the kernel test bot
Added a new flag PPMU_P10 and used it instead of PPMU_ARCH_31 to restrict
the changes to the current platform (Power10)
v1 patch link:
https://lore.kernel.org/linuxppc-dev/20240511075344.1393631-1-anjalik@linux.ibm.com/
arch/powerpc/include/asm/perf_event_server.h | 3 +-
arch/powerpc/perf/core-book3s.c | 45 +++++++++-----------
arch/powerpc/perf/power10-pmu.c | 3 +-
3 files changed, 23 insertions(+), 28 deletions(-)
diff --git a/arch/powerpc/include/asm/perf_event_server.h b/arch/powerpc/include/asm/perf_event_server.h
index e2221d29fdf9..5995614e9062 100644
--- a/arch/powerpc/include/asm/perf_event_server.h
+++ b/arch/powerpc/include/asm/perf_event_server.h
@@ -89,7 +89,8 @@ struct power_pmu {
#define PPMU_NO_SIAR 0x00000100 /* Do not use SIAR */
#define PPMU_ARCH_31 0x00000200 /* Has MMCR3, SIER2 and SIER3 */
#define PPMU_P10_DD1 0x00000400 /* Is power10 DD1 processor version */
-#define PPMU_HAS_ATTR_CONFIG1 0x00000800 /* Using config1 attribute */
+#define PPMU_P10 0x00000800 /* For power10 pmu */
+#define PPMU_HAS_ATTR_CONFIG1 0x00001000 /* Using config1 attribute */
/*
* Values for flags to get_alternatives()
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index 6b5f8a94e7d8..42867469752d 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -266,31 +266,12 @@ static inline u32 perf_flags_from_msr(struct pt_regs *regs)
static inline u32 perf_get_misc_flags(struct pt_regs *regs)
{
bool use_siar = regs_use_siar(regs);
- unsigned long mmcra = regs->dsisr;
- int marked = mmcra & MMCRA_SAMPLE_ENABLE;
+ unsigned long siar;
+ unsigned long addr;
if (!use_siar)
return perf_flags_from_msr(regs);
- /*
- * Check the address in SIAR to identify the
- * privilege levels since the SIER[MSR_HV, MSR_PR]
- * bits are not set for marked events in power10
- * DD1.
- */
- if (marked && (ppmu->flags & PPMU_P10_DD1)) {
- 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;
- }
- }
-
/*
* If we don't have flags in MMCRA, rather than using
* the MSR, we intuit the flags from the address in
@@ -298,19 +279,31 @@ static inline u32 perf_get_misc_flags(struct pt_regs *regs)
* results
*/
if (ppmu->flags & PPMU_NO_SIPR) {
- unsigned long siar = mfspr(SPRN_SIAR);
+ siar = mfspr(SPRN_SIAR);
if (is_kernel_addr(siar))
return PERF_RECORD_MISC_KERNEL;
return PERF_RECORD_MISC_USER;
}
/* PR has priority over HV, so order below is important */
- if (regs_sipr(regs))
- return PERF_RECORD_MISC_USER;
-
- if (regs_sihv(regs) && (freeze_events_kernel != MMCR0_FCHV))
+ if (regs_sipr(regs)) {
+ if (!(ppmu->flags & PPMU_P10))
+ return PERF_RECORD_MISC_USER;
+ } else if (regs_sihv(regs) && (freeze_events_kernel != MMCR0_FCHV))
return PERF_RECORD_MISC_HYPERVISOR;
+ /*
+ * Check the address in SIAR to identify the
+ * privilege levels since the SIER[MSR_HV, MSR_PR]
+ * bits are not set correctly in power10 sometimes
+ */
+ if (ppmu->flags & PPMU_P10) {
+ siar = mfspr(SPRN_SIAR);
+ addr = siar ? siar : regs->nip;
+ if (!is_kernel_addr(addr))
+ return PERF_RECORD_MISC_USER;
+ }
+
return PERF_RECORD_MISC_KERNEL;
}
diff --git a/arch/powerpc/perf/power10-pmu.c b/arch/powerpc/perf/power10-pmu.c
index 62a68b6b2d4b..bb57b7cfe640 100644
--- a/arch/powerpc/perf/power10-pmu.c
+++ b/arch/powerpc/perf/power10-pmu.c
@@ -593,7 +593,8 @@ static struct power_pmu power10_pmu = {
.get_mem_weight = isa207_get_mem_weight,
.disable_pmc = isa207_disable_pmc,
.flags = PPMU_HAS_SIER | PPMU_ARCH_207S |
- PPMU_ARCH_31 | PPMU_HAS_ATTR_CONFIG1,
+ PPMU_ARCH_31 | PPMU_HAS_ATTR_CONFIG1 |
+ PPMU_P10,
.n_generic = ARRAY_SIZE(power10_generic_events),
.generic_events = power10_generic_events,
.cache_events = &power10_cache_events,
base-commit: 1613e604df0cd359cf2a7fbd9be7a0bcfacfabd0
--
2.39.3
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