mirrors
/
linux-stable
mirror of https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
1
0
Fork 0
Code Issues Releases Wiki Activity

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 <pmartincic@microsoft.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Link: https://lore.kernel.org/r/20231127213524.52783-1-pmartincic@linux.microsoft.com
Signed-off-by: Wei Liu <wei.liu@kernel.org>
Message-ID: <20231127213524.52783-1-pmartincic@linux.microsoft.com>
This commit is contained in:
Peter Martincic 2023-11-27 13:35:24 -08:00 committed by Wei Liu
parent d206a76d7d
commit adf47524b5
1 changed files with 30 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

31
drivers/hv/hv_util.c
View File

@ -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);
}