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From:   Dexuan Cui <decui@microsoft.com>
To:     "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>,
        Michael Kelley <mikelley@microsoft.com>,
        "tglx@linutronix.de" <tglx@linutronix.de>
CC:     "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        Dexuan Cui <decui@microsoft.com>
Subject: [PATCH v2 2/7] clocksource/drivers: Suspend/resume Hyper-V
 clocksource for hibernation
Thread-Topic: [PATCH v2 2/7] clocksource/drivers: Suspend/resume Hyper-V
 clocksource for hibernation
Thread-Index: AQHVR8iouPBk654/00attUBlTQo7kA==
Date:   Wed, 31 Jul 2019 17:52:02 +0000
Message-ID: <1564595464-56520-3-git-send-email-decui@microsoft.com>
References: <1564595464-56520-1-git-send-email-decui@microsoft.com>
In-Reply-To: <1564595464-56520-1-git-send-email-decui@microsoft.com>
Reply-To: Dexuan Cui <decui@microsoft.com>
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This is needed for hibernation, e.g. when we resume the old kernel, we need
to disable the "current" kernel's TSC page and then resume the old kernel's=
.

Signed-off-by: Dexuan Cui <decui@microsoft.com>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
---
 drivers/clocksource/hyperv_timer.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyper=
v_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 *arg)
 	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
--=20
1.8.3.1