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path: root/drivers/clocksource/hyperv_timer.c
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Diffstat (limited to 'drivers/clocksource/hyperv_timer.c')
-rw-r--r--drivers/clocksource/hyperv_timer.c12
1 files changed, 10 insertions, 2 deletions
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 42748adccc98..9d808d595ca8 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -302,6 +302,14 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
* the other that uses the TSC reference page feature as defined in the
* TLFS. The MSR version is for compatibility with old versions of
* Hyper-V and 32-bit x86. The TSC reference page version is preferred.
+ *
+ * The Hyper-V clocksource ratings of 250 are chosen to be below the
+ * TSC clocksource rating of 300. In configurations where Hyper-V offers
+ * an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource
+ * is available and preferred. With the higher rating, it will be the
+ * default. On older hardware and Hyper-V versions, the TSC is marked
+ * "unstable", so no TSC clocksource is created and the selected Hyper-V
+ * clocksource will be the default.
*/
u64 (*hv_read_reference_counter)(void);
@@ -363,7 +371,7 @@ static void resume_hv_clock_tsc(struct clocksource *arg)
static struct clocksource hyperv_cs_tsc = {
.name = "hyperv_clocksource_tsc_page",
- .rating = 400,
+ .rating = 250,
.read = read_hv_clock_tsc_cs,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
@@ -395,7 +403,7 @@ static u64 read_hv_sched_clock_msr(void)
static struct clocksource hyperv_cs_msr = {
.name = "hyperv_clocksource_msr",
- .rating = 400,
+ .rating = 250,
.read = read_hv_clock_msr_cs,
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,