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-rw-r--r--virt/kvm/arm/arch_timer.c31
1 files changed, 31 insertions, 0 deletions
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index ea6064696fe4..a9ad4fe3f68f 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -34,6 +34,11 @@ static struct timecounter *timecounter;
static struct workqueue_struct *wqueue;
static unsigned int host_vtimer_irq;
+void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
+{
+ vcpu->arch.timer_cpu.active_cleared_last = false;
+}
+
static cycle_t kvm_phys_timer_read(void)
{
return timecounter->cc->read(timecounter->cc);
@@ -130,6 +135,7 @@ static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level)
BUG_ON(!vgic_initialized(vcpu->kvm));
+ timer->active_cleared_last = false;
timer->irq.level = new_level;
trace_kvm_timer_update_irq(vcpu->vcpu_id, timer->map->virt_irq,
timer->irq.level);
@@ -245,10 +251,35 @@ void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu)
else
phys_active = false;
+ /*
+ * We want to avoid hitting the (re)distributor as much as
+ * possible, as this is a potentially expensive MMIO access
+ * (not to mention locks in the irq layer), and a solution for
+ * this is to cache the "active" state in memory.
+ *
+ * Things to consider: we cannot cache an "active set" state,
+ * because the HW can change this behind our back (it becomes
+ * "clear" in the HW). We must then restrict the caching to
+ * the "clear" state.
+ *
+ * The cache is invalidated on:
+ * - vcpu put, indicating that the HW cannot be trusted to be
+ * in a sane state on the next vcpu load,
+ * - any change in the interrupt state
+ *
+ * Usage conditions:
+ * - cached value is "active clear"
+ * - value to be programmed is "active clear"
+ */
+ if (timer->active_cleared_last && !phys_active)
+ return;
+
ret = irq_set_irqchip_state(timer->map->irq,
IRQCHIP_STATE_ACTIVE,
phys_active);
WARN_ON(ret);
+
+ timer->active_cleared_last = !phys_active;
}
/**