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powerpc/perf: Set cpumode flags using sample address

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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@linux.ibm.com>
Reviewed-by: Athira Rajeev <atrajeev@linux.vnet.ibm.com <mailto:atrajeev@linux.vnet.ibm.com>>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Link: https://msgid.link/20240528040356.2722275-1-anjalik@linux.ibm.com
This commit is contained in:
Anjali K 2024-05-28 09:33:56 +05:30 committed by Michael Ellerman
parent 2bac6caee9
commit 0300a92e96
3 changed files with 23 additions and 28 deletions
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3
arch/powerpc/include/asm/perf_event_server.h
View File

@ -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()

45
arch/powerpc/perf/core-book3s.c
View File

@ -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;
}

3
arch/powerpc/perf/power10-pmu.c
View File

@ -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,