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

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Message-Id: <20221103152338.2926983-1-anrayabh@linux.microsoft.com>
Date:   Thu,  3 Nov 2022 20:53:37 +0530
From:   Anirudh Rayabharam <anrayabh@...ux.microsoft.com>
To:     "K. Y. 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, kumarpraveen@...ux.microsoft.com,
        Anirudh Rayabharam <anrayabh@...ux.microsoft.com>,
        Michael Kelley <mikelley@...rosoft.com>,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] clocksource/drivers/hyperv: use Hyper-V's page size to calculate PFN

__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