[Qemu-devel] [PATCH v2 3/7] kvm/x86: Hyper-V unify stimer_start() and stimer_restart()

[Andrey Smetanin]

This will be used in future to start Hyper-V SynIC timer
in several places by one logic in one function.

Changes v2:
* drop stimer->count == 0 check inside stimer_start()
* comment stimer_start() assumptions

Signed-off-by: Andrey Smetanin <address@hidden>
Reviewed-by: Roman Kagan <address@hidden>
CC: Gleb Natapov <address@hidden>
CC: Paolo Bonzini <address@hidden>
CC: Roman Kagan <address@hidden>
CC: Denis V. Lunev <address@hidden>
CC: address@hidden
---
 arch/x86/kvm/hyperv.c | 43 ++++++++++++++++++++-----------------------
 1 file changed, 20 insertions(+), 23 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 6b2ed93..0dd7d17 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -408,6 +408,7 @@ static void stimer_cleanup(struct kvm_vcpu_hv_stimer 
*stimer)
        clear_bit(stimer->index,
                  vcpu_to_hv_vcpu(vcpu)->stimer_pending_bitmap);
        stimer->msg_pending = false;
+       stimer->exp_time = 0;
 }
 
 static enum hrtimer_restart stimer_timer_callback(struct hrtimer *timer)
@@ -420,24 +421,11 @@ static enum hrtimer_restart stimer_timer_callback(struct 
hrtimer *timer)
        return HRTIMER_NORESTART;
 }
 
-static void stimer_restart(struct kvm_vcpu_hv_stimer *stimer)
-{
-       u64 time_now;
-       ktime_t ktime_now;
-       u64 remainder;
-
-       time_now = get_time_ref_counter(stimer_to_vcpu(stimer)->kvm);
-       ktime_now = ktime_get();
-
-       div64_u64_rem(time_now - stimer->exp_time, stimer->count, &remainder);
-       stimer->exp_time = time_now + (stimer->count - remainder);
-
-       hrtimer_start(&stimer->timer,
-                     ktime_add_ns(ktime_now,
-                                  100 * (stimer->exp_time - time_now)),
-                     HRTIMER_MODE_ABS);
-}
-
+/*
+ * stimer_start() assumptions:
+ * a) stimer->count is not equal to 0
+ * b) stimer->config has HV_STIMER_ENABLE flag
+ */
 static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)
 {
        u64 time_now;
@@ -447,12 +435,21 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)
        ktime_now = ktime_get();
 
        if (stimer->config & HV_STIMER_PERIODIC) {
-               if (stimer->count == 0)
-                       return -EINVAL;
+               if (stimer->exp_time) {
+                       if (time_now >= stimer->exp_time) {
+                               u64 remainder;
+
+                               div64_u64_rem(time_now - stimer->exp_time,
+                                             stimer->count, &remainder);
+                               stimer->exp_time =
+                                       time_now + (stimer->count - remainder);
+                       }
+               } else
+                       stimer->exp_time = time_now + stimer->count;
 
-               stimer->exp_time = time_now + stimer->count;
                hrtimer_start(&stimer->timer,
-                             ktime_add_ns(ktime_now, 100 * stimer->count),
+                             ktime_add_ns(ktime_now,
+                                          100 * (stimer->exp_time - time_now)),
                              HRTIMER_MODE_ABS);
                return 0;
        }
@@ -580,7 +577,7 @@ static void stimer_expiration(struct kvm_vcpu_hv_stimer 
*stimer)
        if (!(stimer->config & HV_STIMER_PERIODIC))
                stimer->config &= ~HV_STIMER_ENABLE;
        else
-               stimer_restart(stimer);
+               stimer_start(stimer);
 }
 
 void kvm_hv_process_stimers(struct kvm_vcpu *vcpu)
-- 
2.4.3