[PATCH v3 3/5] coresight: etm4x: fix inconsistencies with sysfs configration

Yeoreum Yun
2026-04-12T17:55:29Z

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.

- If a perf session and sysfs session tries to enable concurrently,
configuration from configfs could be corrupted.

- There is chance to corrupt drvdata->config if perf session tries
to enabled among handling cscfg_csdev_disable_active_config()
in etm4_disable_sysfs().

To resolve these inconsistencies, the configuration should be separated into:

- active_config, which is applied configuration for the current session
- config, which stores the settings configured via sysfs.

and apply configuration from configfs after taking a mode.

Signed-off-by: Yeoreum Yun <yeoreum.yun@arm.com>
---
.../hwtracing/coresight/coresight-etm4x-cfg.c | 2 +-
.../coresight/coresight-etm4x-core.c | 74 ++++++++++++-------
drivers/hwtracing/coresight/coresight-etm4x.h | 2 +
3 files changed, 49 insertions(+), 29 deletions(-)

diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
index d14d7c8a23e5..0553771d04e7 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 8ebfd3924143..ba1935decff1 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -245,6 +245,9 @@ void etm4_release_trace_id(struct etmv4_drvdata *drvdata)

struct etm4_enable_arg {
struct etmv4_drvdata *drvdata;
+ unsigned long cfg_hash;
+ int preset;
+ u8 trace_id;
int rc;
};

@@ -270,10 +273,11 @@ 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;
@@ -281,7 +285,7 @@ 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
@@ -292,12 +296,13 @@ 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);
@@ -305,7 +310,7 @@ 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);
@@ -499,7 +504,7 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
{
int i, rc;
const struct etmv4_caps *caps = &drvdata->caps;
- 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;
@@ -616,19 +621,36 @@ static int etm4_enable_hw(struct etmv4_drvdata *drvdata)
static void etm4_enable_sysfs_smp_call(void *info)
{
struct etm4_enable_arg *arg = info;
+ struct etmv4_drvdata *drvdata;
struct coresight_device *csdev;

if (WARN_ON(!arg))
return;

- csdev = arg->drvdata->csdev;
+ drvdata = arg->drvdata;
+ csdev = drvdata->csdev;
if (!coresight_take_mode(csdev, CS_MODE_SYSFS)) {
/* Someone is already using the tracer */
arg->rc = -EBUSY;
return;
}

- arg->rc = etm4_enable_hw(arg->drvdata);
+ drvdata->active_config = drvdata->config;
+
+ if (arg->cfg_hash) {
+ arg->rc = cscfg_csdev_enable_active_config(csdev,
+ arg->cfg_hash,
+ arg->preset);
+ if (arg->rc)
+ return;
+ }
+
+ drvdata->trcid = arg->trace_id;
+
+ /* Tracer will never be paused in sysfs mode */
+ drvdata->paused = false;
+
+ arg->rc = etm4_enable_hw(drvdata);

/* The tracer didn't start */
if (arg->rc)
@@ -670,7 +692,7 @@ static int etm4_config_timestamp_event(struct etmv4_drvdata *drvdata,
int ctridx;
int rselector;
const struct etmv4_caps *caps = &drvdata->caps;
- 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 (!caps->nr_cntr)
@@ -754,7 +776,7 @@ static int etm4_parse_event_config(struct coresight_device *csdev,
int ret = 0;
struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
const struct etmv4_caps *caps = &drvdata->caps;
- 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,
};
@@ -916,24 +938,18 @@ 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);
- 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 */
- drvdata->paused = false;
-
/*
* Executing etm4_enable_hw on the cpu whose ETM is being enabled
* ensures that register writes occur when cpu is powered.
*/
arg.drvdata = drvdata;
+ arg.cfg_hash = cfg_hash;
+ arg.preset = preset;
+ arg.trace_id = path->trace_id;
+
ret = smp_call_function_single(drvdata->cpu,
etm4_enable_sysfs_smp_call, &arg, 1);
if (!ret)
@@ -1034,7 +1050,7 @@ static void etm4_disable_hw(struct etmv4_drvdata *drvdata)
{
u32 control;
const struct etmv4_caps *caps = &drvdata->caps;
- 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;
@@ -1070,6 +1086,8 @@ static void etm4_disable_sysfs_smp_call(void *info)

etm4_disable_hw(drvdata);

+ cscfg_csdev_disable_active_config(drvdata->csdev);
+
coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
}

@@ -1130,9 +1148,6 @@ static void etm4_disable_sysfs(struct coresight_device *csdev)
drvdata, 1);

raw_spin_unlock(&drvdata->spinlock);
-
- cscfg_csdev_disable_active_config(csdev);
-
cpus_read_unlock();

/*
@@ -1375,6 +1390,7 @@ static void etm4_init_arch_data(void *info)
struct etm4_init_arg *init_arg = info;
struct etmv4_drvdata *drvdata;
struct etmv4_caps *caps;
+ struct etmv4_config *config;
struct csdev_access *csa;
struct device *dev = init_arg->dev;
int i;
@@ -1382,6 +1398,7 @@ static void etm4_init_arch_data(void *info)
drvdata = dev_get_drvdata(init_arg->dev);
caps = &drvdata->caps;
csa = init_arg->csa;
+ config = &drvdata->active_config;

/*
* If we are unable to detect the access mechanism,
@@ -1442,7 +1459,7 @@ static void etm4_init_arch_data(void *info)

/* EXLEVEL_S, bits[19:16] Secure state instruction tracing */
caps->s_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_S_MASK, etmidr3);
- drvdata->config.s_ex_level = caps->s_ex_level;
+ config->s_ex_level = caps->s_ex_level;
/* EXLEVEL_NS, bits[23:20] Non-secure state instruction tracing */
caps->ns_ex_level = FIELD_GET(TRCIDR3_EXLEVEL_NS_MASK, etmidr3);
/*
@@ -1687,7 +1704,7 @@ 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
@@ -1728,7 +1745,7 @@ 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)
@@ -2250,7 +2267,8 @@ 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 3cc1ca76c933..b943c28c9c71 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -1069,6 +1069,7 @@ 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
* @paused: Indicates if the trace unit is paused.
@@ -1089,6 +1090,7 @@ struct etmv4_drvdata {
bool os_unlock : 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);