linux-kernel - [PATCH v5 3/3] clocksource/drivers: Suspend/resume Hyper-V clocksource for hibernation

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Date:   Thu, 5 Sep 2019 22:47:15 +0000
From:   Dexuan Cui <decui@...rosoft.com>
To:     "arnd@...db.de" <arnd@...db.de>, "bp@...en8.de" <bp@...en8.de>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        "hpa@...or.com" <hpa@...or.com>, KY Srinivasan <kys@...rosoft.com>,
        "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mingo@...hat.com" <mingo@...hat.com>,
        "sashal@...nel.org" <sashal@...nel.org>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "x86@...nel.org" <x86@...nel.org>,
        Michael Kelley <mikelley@...rosoft.com>,
        Sasha Levin <Alexander.Levin@...rosoft.com>
CC:     "linux-arch@...r.kernel.org" <linux-arch@...r.kernel.org>,
        Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v5 3/3] clocksource/drivers: Suspend/resume Hyper-V
 clocksource for hibernation

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@...rosoft.com>
Reviewed-by: Michael Kelley <mikelley@...rosoft.com>
---
 drivers/clocksource/hyperv_timer.c | 25 +++++++++++++++++++++++++
 1 file changed, 25 insertions(+)

diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 726a65e..07f4747 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -237,12 +237,37 @@ static u64 read_hv_sched_clock_tsc(void)
 	return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
 }
 
+static void suspend_hv_clock_tsc(struct clocksource *arg)
+{
+	u64 tsc_msr;
+
+	/* Disable the TSC page */
+	hv_get_reference_tsc(tsc_msr);
+	tsc_msr &= ~BIT_ULL(0);
+	hv_set_reference_tsc(tsc_msr);
+}
+
+
+static void resume_hv_clock_tsc(struct clocksource *arg)
+{
+	phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
+	u64 tsc_msr;
+
+	/* Re-enable the TSC page */
+	hv_get_reference_tsc(tsc_msr);
+	tsc_msr &= GENMASK_ULL(11, 0);
+	tsc_msr |= BIT_ULL(0) | (u64)phys_addr;
+	hv_set_reference_tsc(tsc_msr);
+}
+
 static struct clocksource hyperv_cs_tsc = {
 	.name	= "hyperv_clocksource_tsc_page",
 	.rating	= 400,
 	.read	= read_hv_clock_tsc,
 	.mask	= CLOCKSOURCE_MASK(64),
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
+	.suspend= suspend_hv_clock_tsc,
+	.resume	= resume_hv_clock_tsc,
 };
 
 static u64 notrace read_hv_clock_msr(struct clocksource *arg)
-- 
1.8.3.1