linux-kernel - RE: [PATCH] clocksource/drivers/hyperv: use Hyper-V's page size to calculate PFN

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Date:   Thu, 3 Nov 2022 15:34:23 +0000
From:   "Michael Kelley (LINUX)" <mikelley@...rosoft.com>
To:     Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Wei Liu <wei.liu@...nel.org>, Dexuan Cui <decui@...rosoft.com>,
        Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>
CC:     "mail@...rudhrb.com" <mail@...rudhrb.com>,
        "kumarpraveen@...ux.microsoft.com" <kumarpraveen@...ux.microsoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: RE: [PATCH] clocksource/drivers/hyperv: use Hyper-V's page size to
 calculate PFN

From: Anirudh Rayabharam <anrayabh@...ux.microsoft.com> Sent: Thursday, November 3, 2022 8:24 AM
> 
> __phys_to_pfn() will return a PFN based on the guest page size, which might
> 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.
> 
> Use HVPFN_DOWN() to calculate the PFN of the TSC page from the physical
> address.
> 
> Reported-by: Michael Kelley (LINUX) <mikelley@...rosoft.com>
> Signed-off-by: Anirudh Rayabharam <anrayabh@...ux.microsoft.com>
> ---
>  drivers/clocksource/hyperv_timer.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_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 *arg)
>  	/* Re-enable the TSC page */
>  	tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC);
>  	tsc_msr.enable = 1;
> -	tsc_msr.pfn = __phys_to_pfn(phys_addr);
> +	tsc_msr.pfn = HVPFN_DOWN(phys_addr);
>  	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);
>  }
> 
> @@ -532,7 +533,7 @@ static bool __init hv_init_tsc_clocksource(void)
>  	 */
>  	tsc_msr.as_uint64 = hv_get_register(HV_REGISTER_REFERENCE_TSC);
>  	tsc_msr.enable = 1;
> -	tsc_msr.pfn = __phys_to_pfn(phys_addr);
> +	tsc_msr.pfn = HVPFN_DOWN(phys_addr);
>  	hv_set_register(HV_REGISTER_REFERENCE_TSC, tsc_msr.as_uint64);
> 
>  	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
> --
> 2.34.1

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