[Qemu-devel] [PATCH v1 6/6] kvm/x86: Update SynIC timers on guest entry only

[Andrey Smetanin]

Consolidate updating the Hyper-V SynIC timers in a
single place: on guest entry in processing KVM_REQ_HV_STIMER
request.  This simplifies the overall logic, and makes sure
the most current state of msrs and guest clock is used for
arming the timers (to achieve that, KVM_REQ_HV_STIMER
has to be processed after KVM_REQ_CLOCK_UPDATE).

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 | 35 +++++++++++++++++------------------
 arch/x86/kvm/x86.c    |  6 ++++++
 2 files changed, 23 insertions(+), 18 deletions(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index d7e6651..7857329 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -389,7 +389,7 @@ static u64 get_time_ref_counter(struct kvm *kvm)
        return div_u64(get_kernel_ns() + kvm->arch.kvmclock_offset, 100);
 }
 
-static void stimer_mark_expired(struct kvm_vcpu_hv_stimer *stimer,
+static void stimer_mark_pending(struct kvm_vcpu_hv_stimer *stimer,
                                bool vcpu_kick)
 {
        struct kvm_vcpu *vcpu = stimer_to_vcpu(stimer);
@@ -417,7 +417,7 @@ static enum hrtimer_restart stimer_timer_callback(struct 
hrtimer *timer)
        struct kvm_vcpu_hv_stimer *stimer;
 
        stimer = container_of(timer, struct kvm_vcpu_hv_stimer, timer);
-       stimer_mark_expired(stimer, true);
+       stimer_mark_pending(stimer, true);
 
        return HRTIMER_NORESTART;
 }
@@ -460,7 +460,7 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)
                 * "If a one shot is enabled and the specified count is in
                 * the past, it will expire immediately."
                 */
-               stimer_mark_expired(stimer, false);
+               stimer_mark_pending(stimer, false);
                return 0;
        }
 
@@ -473,30 +473,24 @@ static int stimer_start(struct kvm_vcpu_hv_stimer *stimer)
 static int stimer_set_config(struct kvm_vcpu_hv_stimer *stimer, u64 config,
                             bool host)
 {
+       stimer_cleanup(stimer);
        if ((stimer->config & HV_STIMER_ENABLE) && HV_STIMER_SINT(config) == 0)
                config &= ~HV_STIMER_ENABLE;
        stimer->config = config;
-       stimer_cleanup(stimer);
-       if (stimer->config & HV_STIMER_ENABLE)
-               if (stimer_start(stimer))
-                       return 1;
+       stimer_mark_pending(stimer, false);
        return 0;
 }
 
 static int stimer_set_count(struct kvm_vcpu_hv_stimer *stimer, u64 count,
                            bool host)
 {
-       stimer->count = count;
-
        stimer_cleanup(stimer);
+       stimer->count = count;
        if (stimer->count == 0)
                stimer->config &= ~HV_STIMER_ENABLE;
-       else if (stimer->config & HV_STIMER_AUTOENABLE) {
+       else if (stimer->config & HV_STIMER_AUTOENABLE)
                stimer->config |= HV_STIMER_ENABLE;
-               if (stimer_start(stimer))
-                       return 1;
-       }
-
+       stimer_mark_pending(stimer, false);
        return 0;
 }
 
@@ -580,16 +574,21 @@ void kvm_hv_process_stimers(struct kvm_vcpu *vcpu)
 {
        struct kvm_vcpu_hv *hv_vcpu = vcpu_to_hv_vcpu(vcpu);
        struct kvm_vcpu_hv_stimer *stimer;
-       u64 time_now;
+       u64 time_now, exp_time;
        int i;
 
        for (i = 0; i < ARRAY_SIZE(hv_vcpu->stimer); i++)
                if (test_and_clear_bit(i, hv_vcpu->stimer_pending_bitmap)) {
                        stimer = &hv_vcpu->stimer[i];
                        if (stimer->config & HV_STIMER_ENABLE) {
-                               time_now = get_time_ref_counter(vcpu->kvm);
-                               if (time_now >= stimer->exp_time)
-                                       stimer_expiration(stimer);
+                               exp_time = stimer->exp_time;
+
+                               if (exp_time) {
+                                       time_now =
+                                               get_time_ref_counter(vcpu->kvm);
+                                       if (time_now >= exp_time)
+                                               stimer_expiration(stimer);
+                               }
 
                                if (stimer->config & HV_STIMER_ENABLE)
                                        stimer_start(stimer);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index b6102c1..795c14c 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -6492,6 +6492,12 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                        r = 0;
                        goto out;
                }
+
+               /*
+                * KVM_REQ_HV_STIMER has to be processed after
+                * KVM_REQ_CLOCK_UPDATE, because Hyper-V SynIC timers
+                * depend on the guest clock being up-to-date
+                */
                if (kvm_check_request(KVM_REQ_HV_STIMER, vcpu))
                        kvm_hv_process_stimers(vcpu);
        }
-- 
2.4.3