From adf47524b56a791734ae24da8412c6579e2fab4f Mon Sep 17 00:00:00 2001 From: Peter Martincic Date: Mon, 27 Nov 2023 13:35:24 -0800 Subject: hv_utils: Allow implicit ICTIMESYNCFLAG_SYNC Hyper-V hosts can omit the _SYNC flag to due a bug on resume from modern suspend. In such a case, the guest may fail to update its time-of-day to account for the period when it was suspended, and could proceed with a significantly wrong time-of-day. In such a case when the guest is significantly behind, fix it by treating a _SAMPLE the same as if _SYNC was received so that the guest time-of-day is updated. This is hidden behind param hv_utils.timesync_implicit. Signed-off-by: Peter Martincic Acked-by: Boqun Feng Link: https://lore.kernel.org/r/20231127213524.52783-1-pmartincic@linux.microsoft.com Signed-off-by: Wei Liu Message-ID: <20231127213524.52783-1-pmartincic@linux.microsoft.com> --- drivers/hv/hv_util.c | 31 ++++++++++++++++++++++++++++++- 1 file changed, 30 insertions(+), 1 deletion(-) (limited to 'drivers/hv') diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c index 42aec2c5606a..9c97c4065fe7 100644 --- a/drivers/hv/hv_util.c +++ b/drivers/hv/hv_util.c @@ -296,6 +296,11 @@ static struct { spinlock_t lock; } host_ts; +static bool timesync_implicit; + +module_param(timesync_implicit, bool, 0644); +MODULE_PARM_DESC(timesync_implicit, "If set treat SAMPLE as SYNC when clock is behind"); + static inline u64 reftime_to_ns(u64 reftime) { return (reftime - WLTIMEDELTA) * 100; @@ -344,6 +349,29 @@ static void hv_set_host_time(struct work_struct *work) do_settimeofday64(&ts); } +/* + * Due to a bug on Hyper-V hosts, the sync flag may not always be sent on resume. + * Force a sync if the guest is behind. + */ +static inline bool hv_implicit_sync(u64 host_time) +{ + struct timespec64 new_ts; + struct timespec64 threshold_ts; + + new_ts = ns_to_timespec64(reftime_to_ns(host_time)); + ktime_get_real_ts64(&threshold_ts); + + threshold_ts.tv_sec += 5; + + /* + * If guest behind the host by 5 or more seconds. + */ + if (timespec64_compare(&new_ts, &threshold_ts) >= 0) + return true; + + return false; +} + /* * Synchronize time with host after reboot, restore, etc. * @@ -384,7 +412,8 @@ static inline void adj_guesttime(u64 hosttime, u64 reftime, u8 adj_flags) spin_unlock_irqrestore(&host_ts.lock, flags); /* Schedule work to do do_settimeofday64() */ - if (adj_flags & ICTIMESYNCFLAG_SYNC) + if ((adj_flags & ICTIMESYNCFLAG_SYNC) || + (timesync_implicit && hv_implicit_sync(host_ts.host_time))) schedule_work(&adj_time_work); } -- cgit