[PATCH 1/2] coresight: etm4x: fix inconsistencies with sysfs configration
From: Yeoreum Yun
Date: Tue Mar 17 2026 - 14:17:35 EST
The current ETM4x configuration via sysfs can lead to the following
inconsistencies:
- If a configuration is modified via sysfs while a perf session is
active, the running configuration may differ between before
a sched-out and after a subsequent sched-in.
- Once a perf session is enabled, some read-only register fields
(e.g., TRCSSCSR<n>) may not be reported correctly,
because drvdata->config is cleared while enabling with perf mode,
even though the information was previously read via etm4_init_arch_data().
To resolve these inconsistencies, the configuration should be separated into:
- active_config, which represents the currently applied configuration
- config, which stores the settings configured via sysfs.
Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
---
.../hwtracing/coresight/coresight-etm4x-cfg.c | 2 +-
.../coresight/coresight-etm4x-core.c | 45 +++++++++++--------
drivers/hwtracing/coresight/coresight-etm4x.h | 2 +
3 files changed, 30 insertions(+), 19 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
index c302072b293a..84213d40d1ae 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
@@ -47,7 +47,7 @@ static int etm4_cfg_map_reg_offset(struct etmv4_drvdata *drvdata,
struct cscfg_regval_csdev *reg_csdev, u32 offset)
{
int err = -EINVAL, idx;
- struct etmv4_config *drvcfg = &drvdata->config;
+ struct etmv4_config *drvcfg = &drvdata->active_config;
u32 off_mask;
if (((offset >= TRCEVENTCTL0R) && (offset <= TRCVIPCSSCTLR)) ||
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index d565a73f0042..c552129c4a0c 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -88,9 +88,11 @@ static int etm4_probe_cpu(unsigned int cpu);
*/
static bool etm4x_sspcicrn_present(struct etmv4_drvdata *drvdata, int n)
{
+ struct etmv4_config *config = &drvdata->active_config;
+
return (n < drvdata->nr_ss_cmp) &&
drvdata->nr_pe &&
- (drvdata->config.ss_status[n] & TRCSSCSRn_PC);
+ (config->ss_status[n] & TRCSSCSRn_PC);
}
u64 etm4x_sysreg_read(u32 offset, bool _relaxed, bool _64bit)
@@ -266,10 +268,11 @@ static void etm4x_prohibit_trace(struct etmv4_drvdata *drvdata)
static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata)
{
u64 trfcr = drvdata->trfcr;
+ struct etmv4_config *config = &drvdata->active_config;
- if (drvdata->config.mode & ETM_MODE_EXCL_KERN)
+ if (config->mode & ETM_MODE_EXCL_KERN)
trfcr &= ~TRFCR_EL1_ExTRE;
- if (drvdata->config.mode & ETM_MODE_EXCL_USER)
+ if (config->mode & ETM_MODE_EXCL_USER)
trfcr &= ~TRFCR_EL1_E0TRE;
return trfcr;
@@ -277,7 +280,7 @@ static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata)
/*
* etm4x_allow_trace - Allow CPU tracing in the respective ELs,
- * as configured by the drvdata->config.mode for the current
+ * as configured by the drvdata->active_config.mode for the current
* session. Even though we have TRCVICTLR bits to filter the
* trace in the ELs, it doesn't prevent the ETM from generating
* a packet (e.g, TraceInfo) that might contain the addresses from
@@ -288,12 +291,13 @@ static u64 etm4x_get_kern_user_filter(struct etmv4_drvdata *drvdata)
static void etm4x_allow_trace(struct etmv4_drvdata *drvdata)
{
u64 trfcr, guest_trfcr;
+ struct etmv4_config *config = &drvdata->active_config;
/* If the CPU doesn't support FEAT_TRF, nothing to do */
if (!drvdata->trfcr)
return;
- if (drvdata->config.mode & ETM_MODE_EXCL_HOST)
+ if (config->mode & ETM_MODE_EXCL_HOST)
trfcr = drvdata->trfcr & ~(TRFCR_EL1_ExTRE | TRFCR_EL1_E0TRE);
else
trfcr = etm4x_get_kern_user_filter(drvdata);
@@ -301,7 +305,7 @@ static void etm4x_allow_trace(struct etmv4_drvdata *drvdata)
write_trfcr(trfcr);
/* Set filters for guests and pass to KVM */
- if (drvdata->config.mode & ETM_MODE_EXCL_GUEST)
+ if (config->mode & ETM_MODE_EXCL_GUEST)
guest_trfcr = drvdata->trfcr & ~(TRFCR_EL1_ExTRE | TRFCR_EL1_E0TRE);
else
guest_trfcr = etm4x_get_kern_user_filter(drvdata);
@@ -494,7 +498,7 @@ static int etm4_enable_trace_unit(struct etmv4_drvdata *drvdata)
static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
{
int i, rc;
- struct etmv4_config *config = &drvdata->config;
+ struct etmv4_config *config = &drvdata->active_config;
struct coresight_device *csdev = drvdata->csdev;
struct device *etm_dev = &csdev->dev;
struct csdev_access *csa = &csdev->access;
@@ -666,7 +670,7 @@ static int etm4_config_timestamp_event(struct etmv4_drvdata *drvdata,
{
int ctridx;
int rselector;
- struct etmv4_config *config = &drvdata->config;
+ struct etmv4_config *config = &drvdata->active_config;
/* No point in trying if we don't have at least one counter */
if (!drvdata->nr_cntr)
@@ -749,7 +753,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
{
int ret = 0;
struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
- struct etmv4_config *config = &drvdata->config;
+ struct etmv4_config *config = &drvdata->active_config;
struct perf_event_attr max_timestamp = {
.ATTR_CFG_FLD_timestamp_CFG = U64_MAX,
};
@@ -911,14 +915,17 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa
/* enable any config activated by configfs */
cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset);
+
+ raw_spin_lock(&drvdata->spinlock);
+
+ drvdata->active_config = drvdata->config;
+
if (cfg_hash) {
ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset);
if (ret)
return ret;
}
- raw_spin_lock(&drvdata->spinlock);
-
drvdata->trcid = path->trace_id;
/* Tracer will never be paused in sysfs mode */
@@ -1028,7 +1035,7 @@ static void etm4_disable_trace_unit(struct etmv4_drvdata *drvdata)
static void etm4_disable_hw(struct etmv4_drvdata *drvdata)
{
u32 control;
- struct etmv4_config *config = &drvdata->config;
+ struct etmv4_config *config = &drvdata->active_config;
struct coresight_device *csdev = drvdata->csdev;
struct csdev_access *csa = &csdev->access;
int i;
@@ -1374,12 +1381,14 @@ static void etm4_init_arch_data(void *info)
u32 etmidr5;
struct etm4_init_arg *init_arg = info;
struct etmv4_drvdata *drvdata;
+ struct etmv4_config *config;
struct csdev_access *csa;
struct device *dev = init_arg->dev;
int i;
drvdata = dev_get_drvdata(init_arg->dev);
csa = init_arg->csa;
+ config = &drvdata->active_config;
/*
* If we are unable to detect the access mechanism,
@@ -1440,7 +1449,7 @@ static void etm4_init_arch_data(void *info)
/* EXLEVEL_S, bits[19:16] Secure state instruction tracing */
drvdata->s_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_S_MASK, etmidr3);
- drvdata->config.s_ex_level = drvdata->s_ex_level;
+ config->s_ex_level = drvdata->s_ex_level;
/* EXLEVEL_NS, bits[23:20] Non-secure state instruction tracing */
drvdata->ns_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_NS_MASK, etmidr3);
/*
@@ -1491,8 +1500,7 @@ static void etm4_init_arch_data(void *info)
*/
drvdata->nr_ss_cmp = FIELD_GET(TRCIDR4_NUMSSCC_MASK, etmidr4);
for (i = 0; i < drvdata->nr_ss_cmp; i++) {
- drvdata->config.ss_status[i] =
- etm4x_relaxed_read32(csa, TRCSSCSRn(i));
+ config->ss_status[i] = etm4x_relaxed_read32(csa, TRCSSCSRn(i));
}
/* NUMCIDC, bits[27:24] number of Context ID comparators for tracing */
drvdata->numcidc = FIELD_GET(TRCIDR4_NUMCIDC_MASK, etmidr4);
@@ -1685,7 +1693,7 @@ static void etm4_set_default(struct etmv4_config *config)
static int etm4_get_next_comparator(struct etmv4_drvdata *drvdata, u32 type)
{
int nr_comparator, index = 0;
- struct etmv4_config *config = &drvdata->config;
+ struct etmv4_config *config = &drvdata->active_config;
/*
* nr_addr_cmp holds the number of comparator _pair_, so time 2
@@ -1726,7 +1734,7 @@ static int etm4_set_event_filters(struct etmv4_drvdata *drvdata,
{
int i, comparator, ret = 0;
u64 address;
- struct etmv4_config *config = &drvdata->config;
+ struct etmv4_config *config = &drvdata->active_config;
struct etm_filters *filters = event->hw.addr_filters;
if (!filters)
@@ -2246,7 +2254,8 @@ static int etm4_add_coresight_dev(struct etm4_init_arg *init_arg)
if (!desc.name)
return -ENOMEM;
- etm4_set_default(&drvdata->config);
+ etm4_set_default(&drvdata->active_config);
+ drvdata->config = drvdata->active_config;
pdata = coresight_get_platform_data(dev);
if (IS_ERR(pdata))
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index 89d81ce4e04e..76beb896f188 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -1022,6 +1022,7 @@ struct etmv4_save_state {
* allows tracing at all ELs. We don't want to compute this
* at runtime, due to the additional setting of TRFCR_CX when
* in EL2. Otherwise, 0.
+ * @active_config: structure holding current applied configuration parameters.
* @config: structure holding configuration parameters.
* @save_state: State to be preserved across power loss
* @skip_power_up: Indicates if an implementation can skip powering up
@@ -1079,6 +1080,7 @@ struct etmv4_drvdata {
bool skip_power_up : 1;
bool paused : 1;
u64 trfcr;
+ struct etmv4_config active_config;
struct etmv4_config config;
struct etmv4_save_state *save_state;
DECLARE_BITMAP(arch_features, ETM4_IMPDEF_FEATURE_MAX);
--
LEVI:{C3F47F37-75D8-414A-A8BA-3980EC8A46D7}