Re: [PATCH v11 3/9] coresight: etm4x: fix inconsistencies with sysfs configuration
From: Mike Leach
Date: Fri Sep 18 2026 - 10:05:36 EST
Hi,
On 9/15/26 12:34, Yeoreum Yun wrote:
The current ETM4x configuration via sysfs can lead to
several inconsistencies:
- If the configuration is modified via sysfs while a perf session is
active, the running configuration may differ before a sched-out and
after a subsequent sched-in.
- If a perf session and a sysfs session enable tracing concurrently,
the configuration from configfs may become corrupted.
- There is a risk of corrupting drvdata->config if a perf session enables
tracing while cscfg_csdev_disable_active_config() is being handled in
etm4_disable_sysfs().
To resolve these issues, separate the configuration into:
- active_config: the configuration applied to the current session
- config: the configuration set via sysfs
I'll add a comment about naming here - active_config is a bit overloaded in the code as it is also used by the csconfig code to represent a loaded and active configuration - which may at some point be applied to the active_config above.
If active_config is for the current session then curr_config would work.
Additionally config also appears as a local pointer in many of the functions. If this is the sysfs config then sysfs_config would work better.
This should make all the code a lot more readable, and easier to spot exactly which config we are dealing with.
Additionally:
- Apply the configuration from configfs after taking the appropriate mode.
- Since active_config and related fields are accessed only by the local CPU
in etm4_enable/disable_sysfs_smp_call() (similar to perf enable/disable),
remove the lock/unlock from the sysfs enable/disable path and
startup/dying_cpu except when to access config fields.
As the active_config is used for cfg-configfs, etmv4 doesn't need to set
its lock for the cfg-configfs since the active_config is proceted by cs_mode
otherwise it would make a possible cpu-stall when it get interrupt while
setting the sysfs configuration.
Therefore, set the drv_spinlock for cfg-configfs as NULL and
let the cfg-configfs disable irq without grap drv_spinlock when it is NULL.
Fixes: 54ff892b76c6 ("coresight: etm4x: splitting struct etmv4_drvdata")
Signed-off-by: Yeoreum Yun <yeoreum.yun@xxxxxxx>
---
drivers/hwtracing/coresight/coresight-config.c | 18 ++--
drivers/hwtracing/coresight/coresight-config.h | 22 ++++
drivers/hwtracing/coresight/coresight-etm4x-cfg.c | 13 ++-
drivers/hwtracing/coresight/coresight-etm4x-core.c | 118 ++++++++++++---------
.../hwtracing/coresight/coresight-etm4x-sysfs.c | 6 +-
drivers/hwtracing/coresight/coresight-etm4x.h | 4 +-
6 files changed, 113 insertions(+), 68 deletions(-)
diff --git a/drivers/hwtracing/coresight/coresight-config.c b/drivers/hwtracing/coresight/coresight-config.c
index 4f72ae71b696e..0e296289f286d 100644
--- a/drivers/hwtracing/coresight/coresight-config.c
+++ b/drivers/hwtracing/coresight/coresight-config.c
@@ -73,13 +73,12 @@ static void cscfg_init_reg_param(struct cscfg_feature_csdev *feat_csdev,
/* set values into the driver locations referenced in cscfg_reg_csdev */
static int cscfg_set_on_enable(struct cscfg_feature_csdev *feat_csdev)
{
- unsigned long flags;
int i;
- raw_spin_lock_irqsave(feat_csdev->drv_spinlock, flags);
- for (i = 0; i < feat_csdev->nr_regs; i++)
- cscfg_set_reg(&feat_csdev->regs_csdev[i]);
- raw_spin_unlock_irqrestore(feat_csdev->drv_spinlock, flags);
+ scoped_guard(feat_csdev_lock, feat_csdev) {
+ for (i = 0; i < feat_csdev->nr_regs; i++)
+ cscfg_set_reg(&feat_csdev->regs_csdev[i]);
+ }
dev_dbg(&feat_csdev->csdev->dev, "Feature %s: %s",
feat_csdev->feat_desc->name, "set on enable");
return 0;
@@ -88,13 +87,12 @@ static int cscfg_set_on_enable(struct cscfg_feature_csdev *feat_csdev)
/* copy back values from the driver locations referenced in cscfg_reg_csdev */
static void cscfg_save_on_disable(struct cscfg_feature_csdev *feat_csdev)
{
- unsigned long flags;
int i;
- raw_spin_lock_irqsave(feat_csdev->drv_spinlock, flags);
- for (i = 0; i < feat_csdev->nr_regs; i++)
- cscfg_save_reg(&feat_csdev->regs_csdev[i]);
- raw_spin_unlock_irqrestore(feat_csdev->drv_spinlock, flags);
+ scoped_guard(feat_csdev_lock, feat_csdev) {
+ for (i = 0; i < feat_csdev->nr_regs; i++)
+ cscfg_save_reg(&feat_csdev->regs_csdev[i]);
+ }
dev_dbg(&feat_csdev->csdev->dev, "Feature %s: %s",
feat_csdev->feat_desc->name, "save on disable");
}
diff --git a/drivers/hwtracing/coresight/coresight-config.h b/drivers/hwtracing/coresight/coresight-config.h
index 90fd937d3bd83..ae6295e308131 100644
--- a/drivers/hwtracing/coresight/coresight-config.h
+++ b/drivers/hwtracing/coresight/coresight-config.h
@@ -7,6 +7,7 @@
#ifndef _CORESIGHT_CORESIGHT_CONFIG_H
#define _CORESIGHT_CORESIGHT_CONFIG_H
+#include <linux/cleanup.h>
#include <linux/coresight.h>
#include <linux/types.h>
@@ -259,4 +260,25 @@ void cscfg_csdev_disable_config(struct cscfg_config_csdev *config_csdev);
/* reset a feature to default values */
void cscfg_reset_feat(struct cscfg_feature_csdev *feat_csdev);
+#define feat_csdev_lock(feat_csdev, flags) \
+ do { \
+ raw_spinlock_t *__lock = feat_csdev->drv_spinlock; \
+ typecheck(unsigned long, flags); \
+ if (__lock) \
+ raw_spin_lock_irqsave(__lock, flags); \
+ } while (0)
+
+#define feat_csdev_unlock(feat_csdev, flags) \
+ do { \
+ raw_spinlock_t *__lock = feat_csdev->drv_spinlock; \
+ typecheck(unsigned long, flags); \
+ if (__lock) \
+ raw_spin_unlock_irqrestore(__lock, flags); \
+ } while (0)
+
+DEFINE_LOCK_GUARD_1(feat_csdev_lock, struct cscfg_feature_csdev,
+ feat_csdev_lock(_T->lock, _T->flags),
+ feat_csdev_unlock(_T->lock, _T->flags),
+ unsigned long flags)
+
#endif /* _CORESIGHT_CORESIGHT_CONFIG_H */
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-cfg.c b/drivers/hwtracing/coresight/coresight-etm4x-cfg.c
index e1a59b4345052..d24f533c623d0 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)) ||
@@ -154,11 +154,14 @@ static int etm4_cfg_load_feature(struct coresight_device *csdev,
int i = 0, err = 0;
/*
- * essential we set the device spinlock - this is used in the generic
- * programming routines when copying values into the drvdata structures
- * via the pointers setup in etm4_cfg_map_reg_offset().
+ * drvdata structure of etm4 for configfs is active_config and
+ * this active_config is protected with csdev->mode by restricting
+ * access to active_config after mode changed to PERF or SYSFS.
+ *
+ * Therefore, it doesn't need to protected with etmv4_drvdata->spinlock
+ * to feature applying and set the NULL.
*/
- feat_csdev->drv_spinlock = &drvdata->spinlock;
+ feat_csdev->drv_spinlock = NULL;
/* process the register descriptions */
for (i = 0; i < feat_csdev->nr_regs && !err; i++) {
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-core.c b/drivers/hwtracing/coresight/coresight-etm4x-core.c
index 2247ad55d4442..2df7f592bb5cf 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-core.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-core.c
@@ -239,6 +239,7 @@ void etm4_release_trace_id(struct etmv4_drvdata *drvdata)
struct etm4_enable_arg {
struct etmv4_drvdata *drvdata;
struct coresight_path *path;
+ struct etmv4_config config;
drvdata contains both active_config and config - why the extra copy here?
int rc;
};
@@ -264,10 +265,11 @@ 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;
@@ -275,7 +277,7 @@ 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
@@ -286,12 +288,13 @@ 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);
@@ -299,7 +302,7 @@ 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);
@@ -492,7 +495,7 @@ 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;
@@ -612,27 +615,44 @@ 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;
+ unsigned long cfg_hash;
+ int preset;
if (WARN_ON(!arg))
return;
- csdev = arg->drvdata->csdev;
- if (!coresight_take_mode(csdev, CS_MODE_SYSFS)) {
- /* Someone is already using the tracer */
- arg->rc = -EBUSY;
- return;
+ drvdata = arg->drvdata;
+ csdev = drvdata->csdev;
+
+ drvdata->active_config = arg->config;
This can happen before the smp call removing the need for arg->config?
+
+ /* enable any config activated by configfs */
+ cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset);
+ if (cfg_hash) {
+ arg->rc = cscfg_csdev_enable_active_config(csdev,
+ cfg_hash,
+ preset);
+ if (arg->rc)
+ return;
}
- arg->rc = etm4_enable_hw(arg->drvdata);
+ drvdata->trcid = arg->path->trace_id;
- /* The tracer didn't start */
+ /* Tracer will never be paused in sysfs mode */
+ drvdata->paused = false;
+
+ arg->rc = etm4_enable_hw(drvdata);
if (arg->rc) {
- coresight_set_mode(csdev, CS_MODE_DISABLED);
+ cscfg_csdev_disable_active_config(csdev);
return;
}
+ drvdata->sticky_enable = true;
csdev->path = arg->path;
+
+ return;
}
/*
@@ -669,7 +689,7 @@ 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)
@@ -752,7 +772,7 @@ 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,
};
@@ -919,46 +939,36 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa
{
struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
struct etm4_enable_arg arg = { };
- unsigned long cfg_hash;
- int ret, preset;
+ int ret;
- /* 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) {
- etm4_release_trace_id(drvdata);
- return ret;
- }
+ if (!coresight_take_mode(csdev, CS_MODE_SYSFS)) {
+ /* Someone is already using the tracer */
+ return -EBUSY;
}
- 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.path = path;
+
+ scoped_guard(raw_spinlock, &drvdata->spinlock) {
+ arg.config = drvdata->config;
Given as mentioned above that once a mode is set then active_config is protected, this should simply be drvdata->active_config = drvdata->config; ??
+ }
+
ret = smp_call_function_single(drvdata->cpu,
etm4_enable_sysfs_smp_call, &arg, 1);
if (!ret)
ret = arg.rc;
- if (!ret)
- drvdata->sticky_enable = true;
-
- if (ret)
+ if (!ret) {
+ dev_dbg(&csdev->dev, "ETM tracing enabled\n");
+ } else {
etm4_release_trace_id(drvdata);
+ /* The tracer didn't start */
+ coresight_set_mode(csdev, CS_MODE_DISABLED);
+ }
- raw_spin_unlock(&drvdata->spinlock);
-
- if (!ret)
- dev_dbg(&csdev->dev, "ETM tracing enabled\n");
return ret;
}
@@ -1044,7 +1054,7 @@ 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;
@@ -1086,8 +1096,9 @@ static void etm4_disable_sysfs_smp_call(void *info)
etm4_disable_hw(drvdata);
+ cscfg_csdev_disable_active_config(drvdata->csdev);
+
drvdata->csdev->path = NULL;
- coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
}
static int etm4_disable_perf(struct coresight_device *csdev,
@@ -1130,8 +1141,9 @@ static int etm4_disable_perf(struct coresight_device *csdev,
static void etm4_disable_sysfs(struct coresight_device *csdev)
{
struct etmv4_drvdata *drvdata = dev_get_drvdata(csdev->dev.parent);
-
- raw_spin_lock(&drvdata->spinlock);
+ struct etmv4_config *config = &drvdata->config;
+ const struct etmv4_config *active_config = &drvdata->active_config;
+ int i;
/*
* Executing etm4_disable_hw on the cpu whose ETM is being disabled
@@ -1140,9 +1152,17 @@ static void etm4_disable_sysfs(struct coresight_device *csdev)
smp_call_function_single(drvdata->cpu, etm4_disable_sysfs_smp_call,
drvdata, 1);
- raw_spin_unlock(&drvdata->spinlock);
+ /*
+ * Userspace may read ss_status and cntr_val through sysfs after
+ * the sysfs-session has been disabled.
+ */
+ for (i = 0; i < drvdata->nr_ss_cmp; i++)
+ config->ss_status[i] = active_config->ss_status[i];
- cscfg_csdev_disable_active_config(csdev);
+ for (i = 0; i < drvdata->nr_cntr; i++)
+ config->cntr_val[i] = active_config->cntr_val[i];
+
Readback of TRCSEQSTR needed here too.
+ coresight_set_mode(drvdata->csdev, CS_MODE_DISABLED);
/*
* we only release trace IDs when resetting sysfs.
@@ -1690,7 +1710,7 @@ 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
@@ -1731,7 +1751,7 @@ 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)
diff --git a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
index 8d73248b840a6..f64c0acebc701 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
+++ b/drivers/hwtracing/coresight/coresight-etm4x-sysfs.c
@@ -1613,7 +1613,7 @@ static ssize_t cntr_val_store(struct device *dev,
return -EINVAL;
if (val > ETM_CNTR_MAX_VAL)
return -EINVAL;
- if (coresight_get_mode(drvdata->csdev))
+ if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS)
return -EBUSY;
raw_spin_lock(&drvdata->spinlock);
@@ -1799,7 +1799,7 @@ static ssize_t sshot_ctrl_store(struct device *dev,
if (kstrtoul(buf, 16, &val))
return -EINVAL;
- if (coresight_get_mode(drvdata->csdev))
+ if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS)
return -EBUSY;
raw_spin_lock(&drvdata->spinlock);
@@ -1851,7 +1851,7 @@ static ssize_t sshot_pe_ctrl_store(struct device *dev,
if (kstrtoul(buf, 16, &val))
return -EINVAL;
- if (coresight_get_mode(drvdata->csdev))
+ if (coresight_get_mode(drvdata->csdev) == CS_MODE_SYSFS)
return -EBUSY;
raw_spin_lock(&drvdata->spinlock);
diff --git a/drivers/hwtracing/coresight/coresight-etm4x.h b/drivers/hwtracing/coresight/coresight-etm4x.h
index df9e0748d71ec..c33700711154d 100644
--- a/drivers/hwtracing/coresight/coresight-etm4x.h
+++ b/drivers/hwtracing/coresight/coresight-etm4x.h
@@ -1019,7 +1019,8 @@ 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.
- * @config: structure holding configuration parameters.
+ * @active_config: structure holding current applied configuration.
+ * @config: structure holding sysfs mode configuration.
* @save_state: State to be preserved across power loss
* @skip_power_up: Indicates if an implementation can skip powering up
* the trace unit.
@@ -1077,6 +1078,7 @@ 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);
Regards
Mike