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From:   "Michael Kelley (LINUX)" <mikelley@microsoft.com>
To:     Anirudh Rayabharam <anrayabh@linux.microsoft.com>,
        KY Srinivasan <kys@microsoft.com>,
        Haiyang Zhang <haiyangz@microsoft.com>,
        Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Thomas Gleixner <tglx@linutronix.de>
CC:     "mail@anirudhrb.com" <mail@anirudhrb.com>,
        "kumarpraveen@linux.microsoft.com" <kumarpraveen@linux.microsoft.com>,
        "linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: RE: [PATCH] clocksource/drivers/hyperv: use Hyper-V's page size to
 calculate PFN
Thread-Topic: [PATCH] clocksource/drivers/hyperv: use Hyper-V's page size to
 calculate PFN
Thread-Index: AQHY75hVmfXQ8ic6FUK0rwzpn+K9rK4tU/gg
Date:   Thu, 3 Nov 2022 15:34:23 +0000
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References: <20221103152338.2926983-1-anrayabh@linux.microsoft.com>
In-Reply-To: <20221103152338.2926983-1-anrayabh@linux.microsoft.com>
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From: Anirudh Rayabharam <anrayabh@linux.microsoft.com> Sent: Thursday, Nov=
ember 3, 2022 8:24 AM
>=20
> __phys_to_pfn() will return a PFN based on the guest page size, which mig=
ht
> be different from Hyper-V's page size that is always 4K. The PFN for the
> TSC page always needs to be a Hyper-V PFN.
>=20
> Use HVPFN_DOWN() to calculate the PFN of the TSC page from the physical
> address.
>=20
> Reported-by: Michael Kelley (LINUX) <mikelley@microsoft.com>
> Signed-off-by: Anirudh Rayabharam <anrayabh@linux.microsoft.com>
> ---
>  drivers/clocksource/hyperv_timer.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
>=20
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyp=
erv_timer.c
> index 11332c82d1af..18de1f439ffd 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -21,6 +21,7 @@
>  #include <linux/interrupt.h>
>  #include <linux/irq.h>
>  #include <linux/acpi.h>
> +#include <linux/hyperv.h>
>  #include <clocksource/hyperv_timer.h>
>  #include <asm/hyperv-tlfs.h>
>  #include <asm/mshyperv.h>
> @@ -412,7 +413,7 @@ static void resume_hv_clock_tsc(struct clocksource *a=
rg)
>  	/* Re-enable the TSC page */
>  	tsc_msr.as_uint64 =3D hv_get_register(HV_REGISTER_REFERENCE_TSC);
>  	tsc_msr.enable =3D 1;
> -	tsc_msr.pfn =3D __phys_to_pfn(phys_addr);
> +	tsc_msr.pfn =3D HVPFN_DOWN(phys_addr);
>  	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);
>  }
>=20
> @@ -532,7 +533,7 @@ static bool __init hv_init_tsc_clocksource(void)
>  	 */
>  	tsc_msr.as_uint64 =3D hv_get_register(HV_REGISTER_REFERENCE_TSC);
>  	tsc_msr.enable =3D 1;
> -	tsc_msr.pfn =3D __phys_to_pfn(phys_addr);
> +	tsc_msr.pfn =3D HVPFN_DOWN(phys_addr);
>  	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);
>=20
>  	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
> --
> 2.34.1

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