[PATCH v3 03/12] clocksource/drivers: Suspend/resume Hyper-V clocksource for hibernation

[Dexuan Cui]

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 <de...@microsoft.com>
Reviewed-by: Michael Kelley <mikel...@microsoft.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 17b96f9..8f3422c 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -238,12 +238,37 @@ static u64 read_hv_clock_tsc(struct clocksource *arg)
        return read_hv_sched_clock_tsc();
 }
 
+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 = page_to_phys(vmalloc_to_page(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,
 };
 #endif
 
-- 
1.8.3.1