kvm/x86: Hyper-V unify stimer_start() and stimer_restart()

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 <asmetanin@virtuozzo.com>
Reviewed-by: Roman Kagan <rkagan@virtuozzo.com>
CC: Gleb Natapov <gleb@kernel.org>
CC: Paolo Bonzini <pbonzini@redhat.com>
CC: Roman Kagan <rkagan@virtuozzo.com>
CC: Denis V. Lunev <den@openvz.org>
CC: qemu-devel@nongnu.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

1 files changed, 20 insertions, 23 deletions

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 6b2ed930bf18..0dd7d1731c22 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)