linux-kernel - Re: [PATCH] x86/Hyper-V: Fix hv sched clock function return wrong time unit

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Message-ID: <87ftdx7nxv.fsf@vitty.brq.redhat.com>
Date:   Tue, 24 Mar 2020 16:49:32 +0100
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     Yubo Xie <ltykernel@...il.com>
Cc:     Yubo Xie <yuboxie@...rosoft.com>, linux-hyperv@...r.kernel.org,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>, kys@...rosoft.com,
        haiyangz@...rosoft.com, sthemmin@...rosoft.com,
        liuwe@...rosoft.com, daniel.lezcano@...aro.org, tglx@...utronix.de,
        michael.h.kelley@...rosoft.com
Subject: Re: [PATCH] x86/Hyper-V: Fix hv sched clock function return wrong time unit

Yubo Xie <ltykernel@...il.com> writes:

> sched clock callback should return time with nano second as unit
> but current hv callback returns time with 100ns. Fix it.
>
> Cc: stable@...r.kernel.org
> Signed-off-by: Yubo Xie <yuboxie@...rosoft.com>
> Signed-off-by: Tianyu Lan <Tianyu.Lan@...rosoft.com>
> Fixes: adb87ff4f96c ("clocksource/drivers/hyperv: Allocate Hyper-V TSC page statically")

I don't think this is the right commit to reference, 

commit bd00cd52d5be655a2f217e2ed74b91a71cb2b14f
Author: Tianyu Lan <Tianyu.Lan@...rosoft.com>
Date:   Wed Aug 14 20:32:16 2019 +0800

    clocksource/drivers/hyperv: Add Hyper-V specific sched clock function

looks like the one.

> ---
>  drivers/clocksource/hyperv_timer.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 9d808d595ca8..662ed978fa24 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -343,7 +343,8 @@ static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
>  
>  static u64 read_hv_sched_clock_tsc(void)
>  {
> -	return read_hv_clock_tsc() - hv_sched_clock_offset;
> +	return (read_hv_clock_tsc() - hv_sched_clock_offset)
> +		* (NSEC_PER_SEC / HV_CLOCK_HZ);
>  }
>  
>  static void suspend_hv_clock_tsc(struct clocksource *arg)
> @@ -398,7 +399,8 @@ static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
>  
>  static u64 read_hv_sched_clock_msr(void)
>  {
> -	return read_hv_clock_msr() - hv_sched_clock_offset;
> +	return (read_hv_clock_msr() - hv_sched_clock_offset)
> +		* (NSEC_PER_SEC / HV_CLOCK_HZ);
>  }

kvmclock seems to have the same (pre-patch) code ...

>  
>  static struct clocksource hyperv_cs_msr = {

-- 
Vitaly