From: Christoffer Dall <cdall@linaro.org>
Date: Sun, 18 Jun 2017 00:32:08 -0700
Subject: KVM: arm/arm64: Use separate timer for phys timer emulation
Patch-mainline: v4.15-rc1
Git-commit: f2a2129e0ac8d8fa79c3f85425c36f6e3368f022
References: bsc#1077761

We were using the same hrtimer for emulating the physical timer and for
making sure a blocking VCPU thread would be eventually woken up.  That
worked fine in the previous arch timer design, but as we are about to
actually use the soft timer expire function for the physical timer
emulation, change the logic to use a dedicated hrtimer.

This has the added benefit of not having to cancel any work in the sync
path, which in turn allows us to run the flush and sync with IRQs
disabled.

Note that the hrtimer used to program the host kernel's timer to
generate an exit from the guest when the emulated physical timer fires
never has to inject any work, and to share the soft_timer_cancel()
function with the bg_timer, we change the function to only cancel any
pending work if the pointer to the work struct is not null.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <cdall@linaro.org>
Acked-by: Alexander Graf <agraf@suse.de>
---
 include/kvm/arm_arch_timer.h |    3 +++
 virt/kvm/arm/arch_timer.c    |   21 ++++++++++++++++-----
 2 files changed, 19 insertions(+), 5 deletions(-)

--- a/include/kvm/arm_arch_timer.h
+++ b/include/kvm/arm_arch_timer.h
@@ -48,6 +48,9 @@
 	/* Work queued with the above timer expires */
 	struct work_struct		expired;
 
+	/* Physical timer emulation */
+	struct hrtimer			phys_timer;
+
 	/* Is the timer enabled */
 	bool			enabled;
 };
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -65,7 +65,8 @@
 static void soft_timer_cancel(struct hrtimer *hrt, struct work_struct *work)
 {
 	hrtimer_cancel(hrt);
-	cancel_work_sync(work);
+	if (work)
+		cancel_work_sync(work);
 }
 
 static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
@@ -172,6 +173,12 @@
 	return HRTIMER_NORESTART;
 }
 
+static enum hrtimer_restart kvm_phys_timer_expire(struct hrtimer *hrt)
+{
+	WARN(1, "Timer only used to ensure guest exit - unexpected event.");
+	return HRTIMER_NORESTART;
+}
+
 bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx)
 {
 	u64 cval, now;
@@ -249,7 +256,7 @@
 }
 
 /* Schedule the background timer for the emulated timer. */
-static void kvm_timer_emulate(struct kvm_vcpu *vcpu,
+static void phys_timer_emulate(struct kvm_vcpu *vcpu,
 			      struct arch_timer_context *timer_ctx)
 {
 	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
@@ -261,7 +268,7 @@
 		return;
 
 	/*  The timer has not yet expired, schedule a background timer */
-	soft_timer_start(&timer->bg_timer, kvm_timer_compute_delta(timer_ctx));
+	soft_timer_start(&timer->phys_timer, kvm_timer_compute_delta(timer_ctx));
 }
 
 /*
@@ -414,7 +421,7 @@
 	kvm_timer_update_state(vcpu);
 
 	/* Set the background timer for the physical timer emulation. */
-	kvm_timer_emulate(vcpu, vcpu_ptimer(vcpu));
+	phys_timer_emulate(vcpu, vcpu_ptimer(vcpu));
 
 	if (unlikely(!irqchip_in_kernel(vcpu->kvm)))
 		kvm_timer_flush_hwstate_user(vcpu);
@@ -437,7 +444,7 @@
 	 * This is to cancel the background timer for the physical timer
 	 * emulation if it is set.
 	 */
-	soft_timer_cancel(&timer->bg_timer, &timer->expired);
+	soft_timer_cancel(&timer->phys_timer, NULL);
 
 	/*
 	 * The guest could have modified the timer registers or the timer
@@ -497,6 +504,9 @@
 	hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
 	timer->bg_timer.function = kvm_bg_timer_expire;
 
+	hrtimer_init(&timer->phys_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	timer->phys_timer.function = kvm_phys_timer_expire;
+
 	vtimer->irq.irq = default_vtimer_irq.irq;
 	ptimer->irq.irq = default_ptimer_irq.irq;
 }
@@ -605,6 +615,7 @@
 	struct arch_timer_context *vtimer = vcpu_vtimer(vcpu);
 
 	soft_timer_cancel(&timer->bg_timer, &timer->expired);
+	soft_timer_cancel(&timer->phys_timer, NULL);
 	kvm_vgic_unmap_phys_irq(vcpu, vtimer->irq.irq);
 }