[PATCH net-next v4 2/3] gve: make nic clock reads thread safe

Harshitha Ramamurthy
2026-04-06T23:40:08Z

From: Ankit Garg <nktgrg@google.com>

Add a mutex to protect the shared DMA buffer that receives NIC
timestamp reports. The NIC timestamp will be read from two different
threads: the periodic worker and upcoming `gettimex64`.

Move clock registration to the last step of initialization to ensure
that all data needed by the clock module is initialized before
the clock is exposed to usermode.

Reviewed-by: Joshua Washington <joshwash@google.com>
Signed-off-by: Ankit Garg <nktgrg@google.com>
Signed-off-by: Jordan Rhee <jordanrhee@google.com>
Signed-off-by: Harshitha Ramamurthy <hramamurthy@google.com>
---
Changes in v3:
- Reorder init/teardown to register PTP clock last, and simplify code
- Move ptp-related members from gve_priv to gve_ptp
- Only assign priv->ptp after ptp module is successfully initialized
---
drivers/net/ethernet/google/gve/gve.h | 12 +-
drivers/net/ethernet/google/gve/gve_ethtool.c | 3 +-
drivers/net/ethernet/google/gve/gve_ptp.c | 134 ++++++++----------
3 files changed, 63 insertions(+), 86 deletions(-)

diff --git a/drivers/net/ethernet/google/gve/gve.h b/drivers/net/ethernet/google/gve/gve.h
index 1d66d3834f7e..7b69d0cfc0d5 100644
--- a/drivers/net/ethernet/google/gve/gve.h
+++ b/drivers/net/ethernet/google/gve/gve.h
@@ -792,6 +792,9 @@ struct gve_ptp {
struct ptp_clock_info info;
struct ptp_clock *clock;
struct gve_priv *priv;
+ struct mutex nic_ts_read_lock; /* Protects nic_ts_report */
+ struct gve_nic_ts_report *nic_ts_report;
+ dma_addr_t nic_ts_report_bus;
};

struct gve_priv {
@@ -923,8 +926,6 @@ struct gve_priv {
bool nic_timestamp_supported;
struct gve_ptp *ptp;
struct kernel_hwtstamp_config ts_config;
- struct gve_nic_ts_report *nic_ts_report;
- dma_addr_t nic_ts_report_bus;
u64 last_sync_nic_counter; /* Clock counter from last NIC TS report */
};

@@ -1201,7 +1202,7 @@ static inline bool gve_supports_xdp_xmit(struct gve_priv *priv)

static inline bool gve_is_clock_enabled(struct gve_priv *priv)
{
- return priv->nic_ts_report;
+ return priv->ptp;
}

/* gqi napi handler defined in gve_main.c */
@@ -1321,14 +1322,9 @@ int gve_flow_rules_reset(struct gve_priv *priv);
int gve_init_rss_config(struct gve_priv *priv, u16 num_queues);
/* PTP and timestamping */
#if IS_ENABLED(CONFIG_PTP_1588_CLOCK)
-int gve_clock_nic_ts_read(struct gve_priv *priv);
int gve_init_clock(struct gve_priv *priv);
void gve_teardown_clock(struct gve_priv *priv);
#else /* CONFIG_PTP_1588_CLOCK */
-static inline int gve_clock_nic_ts_read(struct gve_priv *priv)
-{
- return -EOPNOTSUPP;
-}

static inline int gve_init_clock(struct gve_priv *priv)
{
diff --git a/drivers/net/ethernet/google/gve/gve_ethtool.c b/drivers/net/ethernet/google/gve/gve_ethtool.c
index dc2213b5ce24..4fd7e8a442c5 100644
--- a/drivers/net/ethernet/google/gve/gve_ethtool.c
+++ b/drivers/net/ethernet/google/gve/gve_ethtool.c
@@ -972,8 +972,7 @@ static int gve_get_ts_info(struct net_device *netdev,
info->rx_filters |= BIT(HWTSTAMP_FILTER_NONE) |
BIT(HWTSTAMP_FILTER_ALL);

- if (priv->ptp)
- info->phc_index = ptp_clock_index(priv->ptp->clock);
+ info->phc_index = ptp_clock_index(priv->ptp->clock);
}

return 0;
diff --git a/drivers/net/ethernet/google/gve/gve_ptp.c b/drivers/net/ethernet/google/gve/gve_ptp.c
index 06b1cf4a5efc..ad15f1209a83 100644
--- a/drivers/net/ethernet/google/gve/gve_ptp.c
+++ b/drivers/net/ethernet/google/gve/gve_ptp.c
@@ -11,19 +11,20 @@
#define GVE_NIC_TS_SYNC_INTERVAL_MS 250

/* Read the nic timestamp from hardware via the admin queue. */
-int gve_clock_nic_ts_read(struct gve_priv *priv)
+static int gve_clock_nic_ts_read(struct gve_ptp *ptp, u64 *nic_raw)
{
- u64 nic_raw;
int err;

- err = gve_adminq_report_nic_ts(priv, priv->nic_ts_report_bus);
+ mutex_lock(&ptp->nic_ts_read_lock);
+ err = gve_adminq_report_nic_ts(ptp->priv, ptp->nic_ts_report_bus);
if (err)
- return err;
+ goto out;

- nic_raw = be64_to_cpu(priv->nic_ts_report->nic_timestamp);
- WRITE_ONCE(priv->last_sync_nic_counter, nic_raw);
+ *nic_raw = be64_to_cpu(ptp->nic_ts_report->nic_timestamp);

- return 0;
+out:
+ mutex_unlock(&ptp->nic_ts_read_lock);
+ return err;
}

static int gve_ptp_gettimex64(struct ptp_clock_info *info,
@@ -41,17 +42,21 @@ static int gve_ptp_settime64(struct ptp_clock_info *info,

static long gve_ptp_do_aux_work(struct ptp_clock_info *info)
{
- const struct gve_ptp *ptp = container_of(info, struct gve_ptp, info);
+ struct gve_ptp *ptp = container_of(info, struct gve_ptp, info);
struct gve_priv *priv = ptp->priv;
+ u64 nic_raw;
int err;

if (gve_get_reset_in_progress(priv) || !gve_get_admin_queue_ok(priv))
goto out;

- err = gve_clock_nic_ts_read(priv);
- if (err && net_ratelimit())
- dev_err(&priv->pdev->dev,
- "%s read err %d\n", __func__, err);
+ err = gve_clock_nic_ts_read(ptp, &nic_raw);
+ if (err) {
+ dev_err_ratelimited(&priv->pdev->dev, "%s read err %d\n",
+ __func__, err);
+ goto out;
+ }
+ WRITE_ONCE(priv->last_sync_nic_counter, nic_raw);

out:
return msecs_to_jiffies(GVE_NIC_TS_SYNC_INTERVAL_MS);
@@ -65,94 +70,71 @@ static const struct ptp_clock_info gve_ptp_caps = {
.do_aux_work = gve_ptp_do_aux_work,
};

-static int gve_ptp_init(struct gve_priv *priv)
+int gve_init_clock(struct gve_priv *priv)
{
struct gve_ptp *ptp;
+ u64 nic_raw;
int err;

- priv->ptp = kzalloc_obj(*priv->ptp);
- if (!priv->ptp)
+ ptp = kzalloc_obj(*priv->ptp);
+ if (!ptp)
return -ENOMEM;

- ptp = priv->ptp;
ptp->info = gve_ptp_caps;
- ptp->clock = ptp_clock_register(&ptp->info, &priv->pdev->dev);
-
- if (IS_ERR(ptp->clock)) {
- dev_err(&priv->pdev->dev, "PTP clock registration failed\n");
- err = PTR_ERR(ptp->clock);
- goto free_ptp;
- }
-
ptp->priv = priv;
- return 0;
-
-free_ptp:
- kfree(ptp);
- priv->ptp = NULL;
- return err;
-}
-
-static void gve_ptp_release(struct gve_priv *priv)
-{
- struct gve_ptp *ptp = priv->ptp;
-
- if (!ptp)
- return;
-
- if (ptp->clock)
- ptp_clock_unregister(ptp->clock);
-
- kfree(ptp);
- priv->ptp = NULL;
-}
-
-int gve_init_clock(struct gve_priv *priv)
-{
- int err;
-
- err = gve_ptp_init(priv);
- if (err)
- return err;
-
- priv->nic_ts_report =
+ mutex_init(&ptp->nic_ts_read_lock);
+ ptp->nic_ts_report =
dma_alloc_coherent(&priv->pdev->dev,
sizeof(struct gve_nic_ts_report),
- &priv->nic_ts_report_bus,
- GFP_KERNEL);
- if (!priv->nic_ts_report) {
+ &ptp->nic_ts_report_bus, GFP_KERNEL);
+ if (!ptp->nic_ts_report) {
dev_err(&priv->pdev->dev, "%s dma alloc error\n", __func__);
err = -ENOMEM;
- goto release_ptp;
+ goto free_ptp;
}
- err = gve_clock_nic_ts_read(priv);
+
+ err = gve_clock_nic_ts_read(ptp, &nic_raw);
if (err) {
dev_err(&priv->pdev->dev, "failed to read NIC clock %d\n", err);
- goto release_nic_ts_report;
+ goto free_dma_mem;
}
- ptp_schedule_worker(priv->ptp->clock,
+ WRITE_ONCE(priv->last_sync_nic_counter, nic_raw);
+
+ ptp->clock = ptp_clock_register(&ptp->info, &priv->pdev->dev);
+ if (IS_ERR(ptp->clock)) {
+ dev_err(&priv->pdev->dev, "PTP clock registration failed\n");
+ err = PTR_ERR(ptp->clock);
+ goto free_dma_mem;
+ }
+
+ priv->ptp = ptp;
+ ptp_schedule_worker(ptp->clock,
msecs_to_jiffies(GVE_NIC_TS_SYNC_INTERVAL_MS));

return 0;

-release_nic_ts_report:
- dma_free_coherent(&priv->pdev->dev,
- sizeof(struct gve_nic_ts_report),
- priv->nic_ts_report, priv->nic_ts_report_bus);
- priv->nic_ts_report = NULL;
-release_ptp:
- gve_ptp_release(priv);
+free_dma_mem:
+ dma_free_coherent(&priv->pdev->dev, sizeof(struct gve_nic_ts_report),
+ ptp->nic_ts_report, ptp->nic_ts_report_bus);
+ ptp->nic_ts_report = NULL;
+free_ptp:
+ mutex_destroy(&ptp->nic_ts_read_lock);
+ kfree(ptp);
return err;
}

void gve_teardown_clock(struct gve_priv *priv)
{
- gve_ptp_release(priv);
+ struct gve_ptp *ptp = priv->ptp;

- if (priv->nic_ts_report) {
- dma_free_coherent(&priv->pdev->dev,
- sizeof(struct gve_nic_ts_report),
- priv->nic_ts_report, priv->nic_ts_report_bus);
- priv->nic_ts_report = NULL;
- }
+ if (!ptp)
+ return;
+
+ priv->ptp = NULL;
+ ptp_clock_unregister(ptp->clock);
+ dma_free_coherent(&priv->pdev->dev, sizeof(struct gve_nic_ts_report),
+ ptp->nic_ts_report, ptp->nic_ts_report_bus);
+ ptp->nic_ts_report = NULL;
+ mutex_destroy(&ptp->nic_ts_read_lock);
+ kfree(ptp);
}
--
2.53.0.1213.gd9a14994de-goog