Similar to x86, add a new vclock_mode VCLOCK_HVCLOCK, and reuse the
hv_read_tsc_page() for userspace to read tsc page clocksource.

Signed-off-by: Boqun Feng (Microsoft) <redacted>
---
 arch/arm64/include/asm/clocksource.h       |  3 ++-
 arch/arm64/include/asm/mshyperv.h          |  2 +-
 arch/arm64/include/asm/vdso/gettimeofday.h | 19 +++++++++++++++++++
 3 files changed, 22 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/include/asm/clocksource.h b/arch/arm64/include/asm/clocksource.h
index fbe80057468c..c6acd45fe748 100644
--- a/arch/arm64/include/asm/clocksource.h
+++ b/arch/arm64/include/asm/clocksource.h

@@ -4,7 +4,8 @@
 
 #define VCLOCK_NONE	0	/* No vDSO clock available.		*/
 #define VCLOCK_CNTVCT	1	/* vDSO should use cntvcnt		*/
-#define VCLOCK_MAX	1
+#define VCLOCK_HVCLOCK	2	/* vDSO should use vread_hvclock()	*/
+#define VCLOCK_MAX	2
 
 struct arch_clocksource_data {
 	int vclock_mode;

diff --git a/arch/arm64/include/asm/mshyperv.h b/arch/arm64/include/asm/mshyperv.h
index 0afb00e3501d..7c85dd816dca 100644
--- a/arch/arm64/include/asm/mshyperv.h
+++ b/arch/arm64/include/asm/mshyperv.h

@@ -90,7 +90,7 @@ extern void hv_get_vpreg_128(u32 reg, struct hv_get_vp_register_output *result);
 #define hv_set_reference_tsc(val) \
 		hv_set_vpreg(HV_REGISTER_REFERENCE_TSC, val)
 #define hv_set_clocksource_vdso(val) \
-		((val).archdata.vclock_mode = VCLOCK_NONE)
+		((val).archdata.vclock_mode = VCLOCK_HVCLOCK)
 
 #if IS_ENABLED(CONFIG_HYPERV)
 #define hv_enable_stimer0_percpu_irq(irq)	enable_percpu_irq(irq, 0)

diff --git a/arch/arm64/include/asm/vdso/gettimeofday.h b/arch/arm64/include/asm/vdso/gettimeofday.h
index e6e3fe0488c7..7e689b903f4d 100644
--- a/arch/arm64/include/asm/vdso/gettimeofday.h
+++ b/arch/arm64/include/asm/vdso/gettimeofday.h

@@ -67,6 +67,20 @@ int clock_getres_fallback(clockid_t _clkid, struct __kernel_timespec *_ts)
 	return ret;
 }
 
+#ifdef CONFIG_HYPERV_TIMER
+/* This will override the default hv_get_raw_timer() */
+#define hv_get_raw_timer() __arch_counter_get_cntvct()
+#include <clocksource/hyperv_timer.h>
+
+extern struct ms_hyperv_tsc_page
+_hvclock_page __attribute__((visibility("hidden")));
+
+static u64 vread_hvclock(void)
+{
+	return hv_read_tsc_page(&_hvclock_page);
+}
+#endif

+
 static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
 {
 	u64 res;

@@ -78,6 +92,11 @@ static __always_inline u64 __arch_get_hw_counter(s32 clock_mode)
 	if (clock_mode == VCLOCK_NONE)
 		return __VDSO_USE_SYSCALL;
 
+#ifdef CONFIG_HYPERV_TIMER
+	if (likely(clock_mode == VCLOCK_HVCLOCK))
+		return vread_hvclock();