[PATCH v2 10/38] clocksource: hyper-v: Don't save/restore TSC offset when using HV sched_clock

[Sean Christopherson]

Now that Hyper-V overrides the sched_clock save/restore hooks if and only
sched_clock itself is set to the Hyper-V timer, drop the invocation of the
"old" save/restore callbacks.  When the registration of the PV sched_clock
was done separate from overriding the save/restore hooks, it was possible
for Hyper-V to clobber the TSC save/restore callbacks without actually
switching to the Hyper-V timer.

Enabling a PV sched_clock is a one-way street, i.e. the kernel will never
revert to using TSC for sched_clock, and so there is no need to invoke the
TSC save/restore hooks (and if there was, it belongs in common PV code).

Signed-off-by: Sean Christopherson <sea...@google.com>
---
 drivers/clocksource/hyperv_timer.c | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/drivers/clocksource/hyperv_timer.c 
b/drivers/clocksource/hyperv_timer.c
index 5a52d0acf31f..4a21874e91b9 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -524,9 +524,6 @@ static __always_inline void hv_setup_sched_clock(void 
*sched_clock)
 }
 #elif defined CONFIG_PARAVIRT
 static u64 hv_ref_counter_at_suspend;
-static void (*old_save_sched_clock_state)(void);
-static void (*old_restore_sched_clock_state)(void);
-
 /*
  * Hyper-V clock counter resets during hibernation. Save and restore clock
  * offset during suspend/resume, while also considering the time passed
@@ -536,8 +533,6 @@ static void (*old_restore_sched_clock_state)(void);
  */
 static void hv_save_sched_clock_state(void)
 {
-       old_save_sched_clock_state();
-
        hv_ref_counter_at_suspend = hv_read_reference_counter();
 }
 
@@ -550,8 +545,6 @@ static void hv_restore_sched_clock_state(void)
         *                - reference counter (time) now.
         */
        hv_sched_clock_offset -= (hv_ref_counter_at_suspend - 
hv_read_reference_counter());
-
-       old_restore_sched_clock_state();
 }
 
 static __always_inline void hv_setup_sched_clock(void *sched_clock)
@@ -559,10 +552,7 @@ static __always_inline void hv_setup_sched_clock(void 
*sched_clock)
        /* We're on x86/x64 *and* using PV ops */
        paravirt_set_sched_clock(sched_clock);
 
-       old_save_sched_clock_state = x86_platform.save_sched_clock_state;
        x86_platform.save_sched_clock_state = hv_save_sched_clock_state;
-
-       old_restore_sched_clock_state = x86_platform.restore_sched_clock_state;
        x86_platform.restore_sched_clock_state = hv_restore_sched_clock_state;
 }
 #else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */
-- 
2.48.1.711.g2feabab25a-goog