clocksource/drivers/hyper-v: Handle sched_clock differences inline

While the Hyper-V Reference TSC code is architecture neutral, the
pv_ops.time.sched_clock() function is implemented for x86/x64, but not
for ARM64. Current code calls a utility function under arch/x86 (and
coming, under arch/arm64) to handle the difference.

Change this approach to handle the difference inline based on whether
GENERIC_SCHED_CLOCK is present.  The new approach removes code under
arch/* since the difference is tied more to the specifics of the Linux
implementation than to the architecture.

No functional change.
Signed-off-by: Michael Kelley <mikelley@microsoft.com>
Reviewed-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Link: https://lore.kernel.org/r/1614721102-2241-9-git-send-email-mikelley@microsoft.comSigned-off-by: Wei Liu <wei.liu@kernel.org>

arch/x86/include/asm/mshyperv.h

@@ -29,17 +29,6 @@ static inline u64 hv_get_register(unsigned int reg)
 
 #define hv_get_raw_timer() rdtsc_ordered()
 
-/*
- * Reference to pv_ops must be inline so objtool
- * detection of noinstr violations can work correctly.
- */
-static __always_inline void hv_setup_sched_clock(void *sched_clock)
-{
-#ifdef CONFIG_PARAVIRT
-	pv_ops.time.sched_clock = sched_clock;
-#endif
-}
-
 void hyperv_vector_handler(struct pt_regs *regs);
 
 static inline void hv_enable_stimer0_percpu_irq(int irq) {}

drivers/clocksource/hyperv_timer.c

@@ -423,6 +423,30 @@ static struct clocksource hyperv_cs_msr = {
 	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
 };
 
+/*
+ * Reference to pv_ops must be inline so objtool
+ * detection of noinstr violations can work correctly.
+ */
+#ifdef CONFIG_GENERIC_SCHED_CLOCK
+static __always_inline void hv_setup_sched_clock(void *sched_clock)
+{
+	/*
+	 * We're on an architecture with generic sched clock (not x86/x64).
+	 * The Hyper-V sched clock read function returns nanoseconds, not
+	 * the normal 100ns units of the Hyper-V synthetic clock.
+	 */
+	sched_clock_register(sched_clock, 64, NSEC_PER_SEC);
+}
+#elif defined CONFIG_PARAVIRT
+static __always_inline void hv_setup_sched_clock(void *sched_clock)
+{
+	/* We're on x86/x64 *and* using PV ops */
+	pv_ops.time.sched_clock = sched_clock;
+}
+#else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */
+static __always_inline void hv_setup_sched_clock(void *sched_clock) {}
+#endif /* CONFIG_GENERIC_SCHED_CLOCK */
+
 static bool __init hv_init_tsc_clocksource(void)
 {
 	u64		tsc_msr;