KVM: arm/arm64: Set a background timer to the earliest timer expiration

When scheduling a background timer, consider both of the virtual and
physical timer and pick the earliest expiration time.

Signed-off-by: Jintack Lim <jintack@cs.columbia.edu>
Reviewed-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

2 files changed, 42 insertions, 14 deletions

diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c
index 0ecd6cf362fc..21c493a9e5c9 100644
--- a/arch/arm/kvm/arm.c
+++ b/arch/arm/kvm/arm.c
@@ -300,7 +300,8 @@ void kvm_arch_vcpu_destroy(struct kvm_vcpu *vcpu)
 
 int kvm_cpu_has_pending_timer(struct kvm_vcpu *vcpu)
 {
-        return kvm_timer_should_fire(vcpu_vtimer(vcpu));
+        return kvm_timer_should_fire(vcpu_vtimer(vcpu)) ||
+               kvm_timer_should_fire(vcpu_ptimer(vcpu));
 }
 
 void kvm_arch_vcpu_blocking(struct kvm_vcpu *vcpu)
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 7f9a66419991..0ea745290871 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -118,6 +118,35 @@ static u64 kvm_timer_compute_delta(struct arch_timer_context *timer_ctx)
         return 0;
 }
 
+static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx)
+{
+        return !(timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_IT_MASK) &&
+                (timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_ENABLE);
+}
+
+/*
+ * Returns the earliest expiration time in ns among guest timers.
+ * Note that it will return 0 if none of timers can fire.
+ */
+static u64 kvm_timer_earliest_exp(struct kvm_vcpu *vcpu)
+{
+        u64 min_virt = ULLONG_MAX, min_phys = ULLONG_MAX;
+        struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
+        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
+
+        if (kvm_timer_irq_can_fire(vtimer))
+                min_virt = kvm_timer_compute_delta(vtimer);
+
+        if (kvm_timer_irq_can_fire(ptimer))
+                min_phys = kvm_timer_compute_delta(ptimer);
+
+        /* If none of timers can fire, then return 0 */
+        if ((min_virt == ULLONG_MAX) && (min_phys == ULLONG_MAX))
+                return 0;
+
+        return min(min_virt, min_phys);
+}
+
 static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
 {
         struct arch_timer_cpu *timer;
@@ -132,7 +161,7 @@ static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
          * PoV (NTP on the host may have forced it to expire
          * early). If we should have slept longer, restart it.
          */
-        ns = kvm_timer_compute_delta(vcpu_vtimer(vcpu));
+        ns = kvm_timer_earliest_exp(vcpu);
         if (unlikely(ns)) {
                 hrtimer_forward_now(hrt, ns_to_ktime(ns));
                 return HRTIMER_RESTART;
@@ -142,12 +171,6 @@ static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
         return HRTIMER_NORESTART;
 }
 
-static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx)
-{
-        return !(timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_IT_MASK) &&
-                (timer_ctx->cnt_ctl & ARCH_TIMER_CTRL_ENABLE);
-}
-
 bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
 {
         u64 cval, now;
@@ -215,26 +238,30 @@ void kvm_timer_schedule(struct kvm_vcpu *vcpu)
 {
         struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
         struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
+        struct arch_timer_context *ptimer = vcpu_ptimer(vcpu);
 
         BUG_ON(timer_is_armed(timer));
 
         /*
-         * No need to schedule a background timer if the guest timer has
+         * No need to schedule a background timer if any guest timer has
          * already expired, because kvm_vcpu_block will return before putting
          * the thread to sleep.
          */
-        if (kvm_timer_should_fire(vtimer))
+        if (kvm_timer_should_fire(vtimer) || kvm_timer_should_fire(ptimer))
                 return;
 
         /*
-         * If the timer is not capable of raising interrupts (disabled or
+         * If both timers are not capable of raising interrupts (disabled or
          * masked), then there's no more work for us to do.
          */
-        if (!kvm_timer_irq_can_fire(vtimer))
+        if (!kvm_timer_irq_can_fire(vtimer) && !kvm_timer_irq_can_fire(ptimer))
                 return;
 
-        /*  The timer has not yet expired, schedule a background timer */
-        timer_arm(timer, kvm_timer_compute_delta(vtimer));
+        /*
+         * The guest timers have not yet expired, schedule a background timer.
+         * Set the earliest expiration time among the guest timers.
+         */
+        timer_arm(timer, kvm_timer_earliest_exp(vcpu));
 }
 
 void kvm_timer_unschedule(struct kvm_vcpu *vcpu)