KVM: arm/arm64: Remove arch timer workqueue

The use of a work queue in the hrtimer expire function for the bg_timer
is a leftover from the time when we would inject interrupts when the
bg_timer expired.

Since we are no longer doing that, we can instead call
kvm_vcpu_wake_up() directly from the hrtimer function and remove all
workqueue functionality from the arch timer code.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@arm.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

include/kvm/arm_arch_timer.h

@@ -21,7 +21,6 @@
 
 #include <linux/clocksource.h>
 #include <linux/hrtimer.h>
-#include <linux/workqueue.h>
 
 struct arch_timer_context {
 	/* Registers: control register, timer value */
@@ -52,9 +51,6 @@ struct arch_timer_cpu {
 	/* Background timer used when the guest is not running */
 	struct hrtimer			bg_timer;
 
-	/* Work queued with the above timer expires */
-	struct work_struct		expired;
-
 	/* Physical timer emulation */
 	struct hrtimer			phys_timer;
 

virt/kvm/arm/arch_timer.c

@@ -70,11 +70,9 @@ static void soft_timer_start(struct hrtimer *hrt, u64 ns)
 		      HRTIMER_MODE_ABS);
 }
 
-static void soft_timer_cancel(struct hrtimer *hrt, struct work_struct *work)
+static void soft_timer_cancel(struct hrtimer *hrt)
 {
 	hrtimer_cancel(hrt);
-	if (work)
-		cancel_work_sync(work);
 }
 
 static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
@@ -102,23 +100,6 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
 	return IRQ_HANDLED;
 }
 
-/*
- * Work function for handling the backup timer that we schedule when a vcpu is
- * no longer running, but had a timer programmed to fire in the future.
- */
-static void kvm_timer_inject_irq_work(struct work_struct *work)
-{
-	struct kvm_vcpu *vcpu;
-
-	vcpu = container_of(work, struct kvm_vcpu, arch.timer_cpu.expired);
-
-	/*
-	 * If the vcpu is blocked we want to wake it up so that it will see
-	 * the timer has expired when entering the guest.
-	 */
-	kvm_vcpu_wake_up(vcpu);
-}
-
 static u64 kvm_timer_compute_delta(struct arch_timer_context *timer_ctx)
 {
 	u64 cval, now;
@@ -188,7 +169,7 @@ static enum hrtimer_restart kvm_bg_timer_expire(struct hrtimer *hrt)
 		return HRTIMER_RESTART;
 	}
 
-	schedule_work(&timer->expired);
+	kvm_vcpu_wake_up(vcpu);
 	return HRTIMER_NORESTART;
 }
 
@@ -300,7 +281,7 @@ static void phys_timer_emulate(struct kvm_vcpu *vcpu)
 	 * then we also don't need a soft timer.
 	 */
 	if (kvm_timer_should_fire(ptimer) || !kvm_timer_irq_can_fire(ptimer)) {
-		soft_timer_cancel(&timer->phys_timer, NULL);
+		soft_timer_cancel(&timer->phys_timer);
 		return;
 	}
 
@@ -426,7 +407,7 @@ void kvm_timer_unschedule(struct kvm_vcpu *vcpu)
 
 	vtimer_restore_state(vcpu);
 
-	soft_timer_cancel(&timer->bg_timer, &timer->expired);
+	soft_timer_cancel(&timer->bg_timer);
 }
 
 static void set_cntvoff(u64 cntvoff)
@@ -544,7 +525,7 @@ void kvm_timer_vcpu_put(struct kvm_vcpu *vcpu)
 	 * In any case, we re-schedule the hrtimer for the physical timer when
 	 * coming back to the VCPU thread in kvm_timer_vcpu_load().
 	 */
-	soft_timer_cancel(&timer->phys_timer, NULL);
+	soft_timer_cancel(&timer->phys_timer);
 
 	/*
 	 * The kernel may decide to run userspace after calling vcpu_put, so
@@ -637,7 +618,6 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
 	update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
 	vcpu_ptimer(vcpu)->cntvoff = 0;
 
-	INIT_WORK(&timer->expired, kvm_timer_inject_irq_work);
 	hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 	timer->bg_timer.function = kvm_bg_timer_expire;
 
@@ -794,8 +774,8 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
 	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 
-	soft_timer_cancel(&timer->bg_timer, &timer->expired);
-	soft_timer_cancel(&timer->phys_timer, NULL);
+	soft_timer_cancel(&timer->bg_timer);
+	soft_timer_cancel(&timer->phys_timer);
 	kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
 }