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Subject[PATCH v1 5/5] perf,kvm/arm64: perf-kvm-stat to report VM TRAP
Date
When guest exits due to "TRAP", we can analyze the guest exit reasons
deeplier. Enhance perf-kvm-stat to record and analyze VM TRAP events.

There is a mapping between guest's "trap_code" (ESR_ELx's bits[31:26])
and "trap_reason" - kvm_arm_exception_class. Copy it from kernel to
aarch64_guest_exits.h, export it to userspace.

This patch records two new KVM tracepoints: "kvm:kvm_trap_enter" and
"kvm:kvm_trap_exit", and reports statistical data between these two
tracepoints.

A simple test go below:

# ./tools/perf/perf kvm stat record -p 20763
[ perf record: Woken up 92 times to write data ]
[ perf record: Captured and wrote 203.727 MB perf.data.guest (2601786 samples) ]

# ./tools/perf/perf kvm stat report --event=vmexit

Analyze events for all VMs, all VCPUs:

VM-EXIT Samples Samples% Time% Min Time Max Time Avg time

TRAP 640931 97.12% 100.00% 2.44us 14683.86us 3446.49us ( +- 0.05% )
IRQ 19019 2.88% 0.00% 0.90us 461.94us 2.12us ( +- 2.09% )

Total Samples:659950, Total events handled time:2209005391.30us.

# ./tools/perf/perf kvm stat report --event=trap

Analyze events for all VMs, all VCPUs:

TRAP-EVENT Samples Samples% Time% Min Time Max Time Avg time

WFx 601194 93.80% 99.98% 0.90us 4294.04us 3671.01us ( +- 0.03% )
SYS64 33714 5.26% 0.01% 1.10us 41.34us 5.68us ( +- 0.18% )
DABT_LOW 6014 0.94% 0.00% 1.12us 18.04us 2.57us ( +- 0.91% )
IABT_LOW 12 0.00% 0.01% 12597.76us 14679.96us 12893.61us ( +- 1.34% )

Total Samples:640934, Total events handled time:2207353434.56us.

Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Christoffer Dall <christoffer.dall@arm.com>
Cc: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Zenghui Yu <yuzenghui@huawei.com>
---
tools/perf/arch/arm64/util/aarch64_guest_exits.h | 68 ++++++++++++++++++++++++
tools/perf/arch/arm64/util/kvm-stat.c | 65 ++++++++++++++++++++++
2 files changed, 133 insertions(+)

diff --git a/tools/perf/arch/arm64/util/aarch64_guest_exits.h b/tools/perf/arch/arm64/util/aarch64_guest_exits.h
index a8ca4b8..0dbbd87 100644
--- a/tools/perf/arch/arm64/util/aarch64_guest_exits.h
+++ b/tools/perf/arch/arm64/util/aarch64_guest_exits.h
@@ -20,4 +20,72 @@
{ARM_EXCEPTION_TRAP, "TRAP" }, \
{ARM_EXCEPTION_HYP_GONE, "HYP_GONE" }

+/* esr.h */
+#define ESR_ELx_EC_UNKNOWN (0x00)
+#define ESR_ELx_EC_WFx (0x01)
+/* Unallocated EC: 0x02 */
+#define ESR_ELx_EC_CP15_32 (0x03)
+#define ESR_ELx_EC_CP15_64 (0x04)
+#define ESR_ELx_EC_CP14_MR (0x05)
+#define ESR_ELx_EC_CP14_LS (0x06)
+#define ESR_ELx_EC_FP_ASIMD (0x07)
+#define ESR_ELx_EC_CP10_ID (0x08) /* EL2 only */
+#define ESR_ELx_EC_PAC (0x09) /* EL2 and above */
+/* Unallocated EC: 0x0A - 0x0B */
+#define ESR_ELx_EC_CP14_64 (0x0C)
+/* Unallocated EC: 0x0d */
+#define ESR_ELx_EC_ILL (0x0E)
+/* Unallocated EC: 0x0F - 0x10 */
+#define ESR_ELx_EC_SVC32 (0x11)
+#define ESR_ELx_EC_HVC32 (0x12) /* EL2 only */
+#define ESR_ELx_EC_SMC32 (0x13) /* EL2 and above */
+/* Unallocated EC: 0x14 */
+#define ESR_ELx_EC_SVC64 (0x15)
+#define ESR_ELx_EC_HVC64 (0x16) /* EL2 and above */
+#define ESR_ELx_EC_SMC64 (0x17) /* EL2 and above */
+#define ESR_ELx_EC_SYS64 (0x18)
+#define ESR_ELx_EC_SVE (0x19)
+/* Unallocated EC: 0x1A - 0x1E */
+#define ESR_ELx_EC_IMP_DEF (0x1f) /* EL3 only */
+#define ESR_ELx_EC_IABT_LOW (0x20)
+#define ESR_ELx_EC_IABT_CUR (0x21)
+#define ESR_ELx_EC_PC_ALIGN (0x22)
+/* Unallocated EC: 0x23 */
+#define ESR_ELx_EC_DABT_LOW (0x24)
+#define ESR_ELx_EC_DABT_CUR (0x25)
+#define ESR_ELx_EC_SP_ALIGN (0x26)
+/* Unallocated EC: 0x27 */
+#define ESR_ELx_EC_FP_EXC32 (0x28)
+/* Unallocated EC: 0x29 - 0x2B */
+#define ESR_ELx_EC_FP_EXC64 (0x2C)
+/* Unallocated EC: 0x2D - 0x2E */
+#define ESR_ELx_EC_SERROR (0x2F)
+#define ESR_ELx_EC_BREAKPT_LOW (0x30)
+#define ESR_ELx_EC_BREAKPT_CUR (0x31)
+#define ESR_ELx_EC_SOFTSTP_LOW (0x32)
+#define ESR_ELx_EC_SOFTSTP_CUR (0x33)
+#define ESR_ELx_EC_WATCHPT_LOW (0x34)
+#define ESR_ELx_EC_WATCHPT_CUR (0x35)
+/* Unallocated EC: 0x36 - 0x37 */
+#define ESR_ELx_EC_BKPT32 (0x38)
+/* Unallocated EC: 0x39 */
+#define ESR_ELx_EC_VECTOR32 (0x3A) /* EL2 only */
+/* Unallocted EC: 0x3B */
+#define ESR_ELx_EC_BRK64 (0x3C)
+/* Unallocated EC: 0x3D - 0x3F */
+#define ESR_ELx_EC_MAX (0x3F)
+
+/* kvm_arm.h */
+#define ECN(x) { ESR_ELx_EC_##x, #x }
+
+#define kvm_arm_exception_class \
+ ECN(UNKNOWN), ECN(WFx), ECN(CP15_32), ECN(CP15_64), ECN(CP14_MR), \
+ ECN(CP14_LS), ECN(FP_ASIMD), ECN(CP10_ID), ECN(CP14_64), ECN(SVC64), \
+ ECN(HVC64), ECN(SMC64), ECN(SYS64), ECN(IMP_DEF), ECN(IABT_LOW), \
+ ECN(IABT_CUR), ECN(PC_ALIGN), ECN(DABT_LOW), ECN(DABT_CUR), \
+ ECN(SP_ALIGN), ECN(FP_EXC32), ECN(FP_EXC64), ECN(SERROR), \
+ ECN(BREAKPT_LOW), ECN(BREAKPT_CUR), ECN(SOFTSTP_LOW), \
+ ECN(SOFTSTP_CUR), ECN(WATCHPT_LOW), ECN(WATCHPT_CUR), \
+ ECN(BKPT32), ECN(VECTOR32), ECN(BRK64)
+
#endif
diff --git a/tools/perf/arch/arm64/util/kvm-stat.c b/tools/perf/arch/arm64/util/kvm-stat.c
index 5804bc2..afa0fc5 100644
--- a/tools/perf/arch/arm64/util/kvm-stat.c
+++ b/tools/perf/arch/arm64/util/kvm-stat.c
@@ -22,6 +22,7 @@
#include "aarch64_guest_exits.h"

define_exit_reasons_table(arm64_exit_reasons, kvm_arm_exception_type);
+define_exit_reasons_table(arm64_trap_reasons, kvm_arm_exception_class);

static struct kvm_events_ops exit_events = {
.is_begin_event = exit_event_begin,
@@ -36,14 +37,78 @@
const char *kvm_entry_trace = "kvm:kvm_entry";
const char *kvm_exit_trace = "kvm:kvm_exit";

+const char *kvm_trap_reason = "esr_ec";
+const char *kvm_trap_enter_trace = "kvm:kvm_trap_enter";
+const char *kvm_trap_exit_trace = "kvm:kvm_trap_exit";
+
+static void trap_event_get_key(struct perf_evsel *evsel,
+ struct perf_sample *sample,
+ struct event_key *key)
+{
+ key->info = 0;
+ key->key = perf_evsel__intval(evsel, sample, kvm_trap_reason);
+}
+
+static const char *get_trap_reason(u64 exit_code)
+{
+ struct exit_reasons_table *tbl = arm64_trap_reasons;
+
+ while (tbl->reason != NULL) {
+ if (tbl->exit_code == exit_code)
+ return tbl->reason;
+ tbl++;
+ }
+
+ pr_err("Unknown kvm trap exit code: %lld on aarch64\n",
+ (unsigned long long)exit_code);
+ return "UNKNOWN";
+}
+
+static bool trap_event_begin(struct perf_evsel *evsel,
+ struct perf_sample *sample, struct event_key *key)
+{
+ if (!strcmp(evsel->name, kvm_trap_enter_trace)) {
+ trap_event_get_key(evsel, sample, key);
+ return true;
+ }
+
+ return false;
+}
+
+static bool trap_event_end(struct perf_evsel *evsel,
+ struct perf_sample *sample __maybe_unused,
+ struct event_key *key __maybe_unused)
+{
+ return (!strcmp(evsel->name, kvm_trap_exit_trace));
+}
+
+static void trap_event_decode_key(struct perf_kvm_stat *kvm __maybe_unused,
+ struct event_key *key,
+ char *decode)
+{
+ const char *trap_reason = get_trap_reason(key->key);
+
+ scnprintf(decode, decode_str_len, "%s", trap_reason);
+}
+
+static struct kvm_events_ops trap_events = {
+ .is_begin_event = trap_event_begin,
+ .is_end_event = trap_event_end,
+ .decode_key = trap_event_decode_key,
+ .name = "TRAP-EVENT",
+};
+
const char *kvm_events_tp[] = {
"kvm:kvm_entry",
"kvm:kvm_exit",
+ "kvm:kvm_trap_enter",
+ "kvm:kvm_trap_exit",
NULL,
};

struct kvm_reg_events_ops kvm_reg_events_ops[] = {
{ .name = "vmexit", .ops = &exit_events },
+ { .name = "trap", .ops = &trap_events },
{ NULL, NULL },
};

--
1.8.3.1

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