[PATCH net-next v4 0/3] gve: add support for PTP gettimex64

Harshitha Ramamurthy
2026-04-06T23:40:05Z

This patch series adds support to obtain near-simultaneous NIC and
system timestamps with gettimex64. This enables daemons like
chrony and phc2sys to synchronize the system clock to the NIC clock.

GVE does not have direct register access to the NIC hardware clock, so
it must issue an AdminQ command to read the NIC clock. Due to relatively
high latency of AQ commands (~100us), it is necessary for the hypervisor
to sample the system time sandwich inside the AQ command.

The first two patches pave the way for the PTP implementation by
quieting excessive logging and refactoring an existing routine for
thread safety.

When tested inside a GCE C3 VM, this enabled chrony to synchronize the
NIC clock and system clock with sub-microsecond precision.

chronyc tracking
Reference ID : 50484330 (PHC0)
Stratum : 1
Ref time (UTC) : Sat Feb 14 01:53:42 2026
System time : 0.000000001 seconds fast of NTP time
Last offset : -0.000000000 seconds
RMS offset : 0.000000001 seconds
Frequency : 0.686 ppm fast
Residual freq : -0.000 ppm
Skew : 0.001 ppm
Root delay : 0.000000001 seconds
Root dispersion : 0.000000812 seconds
Update interval : 0.5 seconds
Leap status : Normal

---
Changelog:
V4:
- call out change to dev_err_ratelimited() in patch 1 commit message (Jacob Keller)
- Ensure only one log is emitted when command returns GVE_ADMINQ_COMMAND_UNSET (Jacob Keller)
- Link to v3: https://lore.kernel.org/netdev/20260403194427.1830609-1-hramamurthy@google.com/

V3:
- Take system time snapshot inside the mutex
- Return -EOPNOTSUPP if cross-timestamp is requested on an arch other
than x86 or arm64
- Fix initialization to only register PTP clock once all data is
initialized
- Link to v2: https://lore.kernel.org/netdev/20260326224527.1044097-1-hramamurthy@google.com/

V2:
- Fixed compilation warning on ARM by casting to u64
- Link to v1: https://lore.kernel.org/netdev/20260323234829.3185051-1-hramamurthy@google.com/
---

Ankit Garg (1):
gve: make nic clock reads thread safe

Jordan Rhee (2):
gve: skip error logging for retryable AdminQ commands
gve: implement PTP gettimex64

drivers/net/ethernet/google/gve/gve.h | 12 +-
drivers/net/ethernet/google/gve/gve_adminq.c | 27 +-
drivers/net/ethernet/google/gve/gve_adminq.h | 4 +-
drivers/net/ethernet/google/gve/gve_ethtool.c | 3 +-
drivers/net/ethernet/google/gve/gve_ptp.c | 317 +++++++++++++-----
5 files changed, 268 insertions(+), 95 deletions(-)

base-commit: 5446b8691eb8278f10deca92048fad84ffd1e4d5
--
2.53.0.1213.gd9a14994de-goog