linux-kernel - [PATCH v6] clocksource/drivers: Suspend/resume Hyper-V clocksource for hibernation

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Message-Id: <1574233946-48377-1-git-send-email-decui@microsoft.com>
Date:   Tue, 19 Nov 2019 23:12:26 -0800
From:   Dexuan Cui <decui@...rosoft.com>
To:     arnd@...db.de, bp@...en8.de, daniel.lezcano@...aro.org,
        haiyangz@...rosoft.com, hpa@...or.com, kys@...rosoft.com,
        linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org,
        mingo@...hat.com, sashal@...nel.org, sthemmin@...rosoft.com,
        tglx@...utronix.de, x86@...nel.org, mikelley@...rosoft.com,
        Alexander.Levin@...rosoft.com, vkuznets@...hat.com
Cc:     linux-arch@...r.kernel.org, Dexuan Cui <decui@...rosoft.com>
Subject: [PATCH v6] 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>
---

This patch is part of the v5 patchset:
  https://lkml.org/lkml/2019/9/5/1158
  https://lkml.org/lkml/2019/9/5/1161

  Actually v6 is the same as v1 (v2~v5 were posted with the other patches).

  Please pick up this patch into the tip.git tree, probably onto the branch
timers/core.

 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 287d8d58c21a..1aec08e82b7a 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -330,12 +330,37 @@ 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)
-- 
2.19.1