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From:   Michael Kelley <mikelley@microsoft.com>
To:     Dexuan Cui <decui@microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
        Stephen Hemminger <sthemmin@microsoft.com>,
        Sasha Levin <Alexander.Levin@microsoft.com>,
        "sashal@kernel.org" <sashal@kernel.org>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH 2/7] clocksource/drivers: Suspend/resume Hyper-V
 clocksource for hibernation
Thread-Topic: [PATCH 2/7] clocksource/drivers: Suspend/resume Hyper-V
 clocksource for hibernation
Thread-Index: AQHVNhdGDMbLoRwEBkehuKx5BQIVXabj3iaQ
Date:   Tue, 30 Jul 2019 22:23:23 +0000
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From: Dexuan Cui <decui@microsoft.com> Sent: Monday, July 8, 2019 10:29 PM
>=20
> This is needed for hibernation, e.g. when we resume the old kernel, we ne=
ed
> to disable the "current" kernel's TSC page and then resume the old kernel=
's.
>=20
> Signed-off-by: Dexuan Cui <decui@microsoft.com>
> ---
>  drivers/clocksource/hyperv_timer.c | 25 +++++++++++++++++++++++++
>  1 file changed, 25 insertions(+)
>=20
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyp=
erv_timer.c
> index ba2c79e6..41c31a7 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -237,12 +237,37 @@ static u64 read_hv_clock_tsc(struct clocksource *ar=
g)
>  	return read_hv_sched_clock_tsc();
>  }
>=20
> +static void suspend_hv_clock_tsc(struct clocksource *arg)
> +{
> +	u64 tsc_msr;
> +
> +	/* Disable the TSC page */
> +	hv_get_reference_tsc(tsc_msr);
> +	tsc_msr &=3D ~BIT_ULL(0);
> +	hv_set_reference_tsc(tsc_msr);
> +}
> +
> +
> +static void resume_hv_clock_tsc(struct clocksource *arg)
> +{
> +	phys_addr_t phys_addr =3D page_to_phys(vmalloc_to_page(tsc_pg));
> +	u64 tsc_msr;
> +
> +	/* Re-enable the TSC page */
> +	hv_get_reference_tsc(tsc_msr);
> +	tsc_msr &=3D GENMASK_ULL(11, 0);
> +	tsc_msr |=3D BIT_ULL(0) | (u64)phys_addr;
> +	hv_set_reference_tsc(tsc_msr);
> +}
> +
>  static struct clocksource hyperv_cs_tsc =3D {
>  	.name	=3D "hyperv_clocksource_tsc_page",
>  	.rating	=3D 400,
>  	.read	=3D read_hv_clock_tsc,
>  	.mask	=3D CLOCKSOURCE_MASK(64),
>  	.flags	=3D CLOCK_SOURCE_IS_CONTINUOUS,
> +	.suspend=3D suspend_hv_clock_tsc,
> +	.resume	=3D resume_hv_clock_tsc,
>  };
>  #endif
>=20
> --
> 1.8.3.1

Reviewed-by: Michael Kelley <mikelley@microsoft.com>