Re: [PATCH] hv_utils: Allow implicit ICTIMESYNCFLAG_SYNC

[Wei Liu <wei.liu@kernel.org>]

On Fri, Oct 27, 2023 at 08:42:33PM +0000, Peter Martincic wrote:
> From 529fcea5d296c22b1dc6c23d55bd6417794b3cda Mon Sep 17 00:00:00 2001
> From: Peter Martincic <pmartincic@microsoft.com>
> Date: Mon, 16 Oct 2023 16:41:10 -0700
> Subject: [PATCH] hv_utils: Allow implicit ICTIMESYNCFLAG_SYNC
> 
> Windows hosts can omit the _SYNC flag to due a bug on resume from modern
> suspend. If the guest is sufficiently behind, treat a _SAMPLE the same
> as if _SYNC was received.
> 
> This is hidden behind param hv_utils.timesync_implicit.
> 
> Signed-off-by: Peter Martincic <pmartincic@microsoft.com>

Boqun, what do you think about this patch?

> ---
>  drivers/hv/hv_util.c | 31 ++++++++++++++++++++++++++++++-
>  1 file changed, 30 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/hv/hv_util.c b/drivers/hv/hv_util.c
> index 42aec2c5606a..158f5ff4b809 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 Windows hosts, the sync flag may not always be sent on resume.
> + * Force a sync if it's 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);
>  }
> 
> --
> 2.34.1
>