[PATCH 3/5] ARM: KVM: arch_timers: Add guest timer core support

[c.dall@virtualopensystems.com (Christoffer Dall)]

From: Marc Zyngier <marc.zyngier@arm.com>

We can inject a timer interrupt into the guest as a result of
three possible events:
- The virtual timer interrupt has fired while we were still
  executing the guest
- The timer interrupt hasn't fired, but it expired while we
  were doing the world switch
- A hrtimer we programmed earlier has fired

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
---
 arch/arm/include/asm/kvm_arch_timer.h |   52 ++++++++
 arch/arm/kvm/reset.c                  |    9 +
 arch/arm/kvm/timer.c                  |  204 +++++++++++++++++++++++++++++++++
 3 files changed, 264 insertions(+), 1 deletion(-)
 create mode 100644 arch/arm/kvm/timer.c

diff --git a/arch/arm/include/asm/kvm_arch_timer.h b/arch/arm/include/asm/kvm_arch_timer.h
index 513b852..512ee39 100644
--- a/arch/arm/include/asm/kvm_arch_timer.h
+++ b/arch/arm/include/asm/kvm_arch_timer.h
@@ -19,13 +19,63 @@
 #ifndef __ASM_ARM_KVM_ARCH_TIMER_H
 #define __ASM_ARM_KVM_ARCH_TIMER_H
 
+#include <linux/clocksource.h>
+#include <linux/hrtimer.h>
+#include <linux/workqueue.h>
+
 struct arch_timer_kvm {
+#ifdef CONFIG_KVM_ARM_TIMER
+	/* Is the timer enabled */
+	bool			enabled;
+
+	/*
+	 * Virtual offset (kernel access it through cntvoff, HYP code
+	 * access it as two 32bit values).
+	 */
+	union {
+		cycle_t		cntvoff;
+		struct {
+			u32	low; 	/* Restored only */
+			u32	high;  	/* Restored only */
+		} cntvoff32;
+	};
+#endif
 };
 
 struct arch_timer_cpu {
+#ifdef CONFIG_KVM_ARM_TIMER
+	/* Background timer used when the guest is not running */
+	struct hrtimer			timer;
+
+	/* Work queued with the above timer expires */
+	struct work_struct		expired;
+
+	/* Background timer active */
+	bool				armed;
+
+	/* Timer IRQ */
+	const struct kvm_irq_level	*irq;
+
+	/* Registers: control register, timer value */
+	u32				cntv_ctl;	/* Saved/restored */
+	union {
+		cycle_t			cntv_cval;
+		struct {
+			u32		low;		/* Saved/restored */
+			u32		high;		/* Saved/restored */
+		} cntv_cval32;
+	};
+#endif
 };
 
-#ifndef CONFIG_KVM_ARM_TIMER
+#ifdef CONFIG_KVM_ARM_TIMER
+int kvm_timer_hyp_init(void);
+int kvm_timer_init(struct kvm *kvm);
+void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu);
+void kvm_timer_sync_to_cpu(struct kvm_vcpu *vcpu);
+void kvm_timer_sync_from_cpu(struct kvm_vcpu *vcpu);
+void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu);
+#else
 static inline int kvm_timer_hyp_init(void)
 {
 	return 0;
diff --git a/arch/arm/kvm/reset.c b/arch/arm/kvm/reset.c
index 290a13d..bb17def 100644
--- a/arch/arm/kvm/reset.c
+++ b/arch/arm/kvm/reset.c
@@ -37,6 +37,12 @@ static struct kvm_regs a15_regs_reset = {
 	.cpsr = SVC_MODE | PSR_A_BIT | PSR_I_BIT | PSR_F_BIT,
 };
 
+#ifdef CONFIG_KVM_ARM_TIMER
+static const struct kvm_irq_level a15_virt_timer_ppi = {
+	.irq	= 27,	/* A7/A15 specific */
+	.level	= 1,
+};
+#endif
 
 /*******************************************************************************
  * Exported reset function
@@ -59,6 +65,9 @@ int kvm_reset_vcpu(struct kvm_vcpu *vcpu)
 			return -EINVAL;
 		cpu_reset = &a15_regs_reset;
 		vcpu->arch.midr = read_cpuid_id();
+#ifdef CONFIG_KVM_ARM_TIMER
+		vcpu->arch.timer_cpu.irq = &a15_virt_timer_ppi;
+#endif
 		break;
 	default:
 		return -ENODEV;
diff --git a/arch/arm/kvm/timer.c b/arch/arm/kvm/timer.c
new file mode 100644
index 0000000..a241298
--- /dev/null
+++ b/arch/arm/kvm/timer.c
@@ -0,0 +1,204 @@
+/*
+ * Copyright (C) 2012 ARM Ltd.
+ * Author: Marc Zyngier <marc.zyngier@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ */
+
+#include <linux/of_irq.h>
+#include <linux/kvm.h>
+#include <linux/kvm_host.h>
+#include <linux/interrupt.h>
+
+#include <asm/arch_timer.h>
+
+#include <asm/kvm_vgic.h>
+#include <asm/kvm_arch_timer.h>
+
+static struct timecounter *timecounter;
+static struct workqueue_struct *wqueue;
+
+static cycle_t kvm_phys_timer_read(void)
+{
+	return timecounter->cc->read(timecounter->cc);
+}
+
+static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	timer->cntv_ctl |= 1 << 1; /* Mask the interrupt in the guest */
+	kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id,
+			    vcpu->arch.timer_cpu.irq->irq,
+			    vcpu->arch.timer_cpu.irq->level);
+}
+
+static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
+{
+	struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id;
+
+	/*
+	 * We disable the timer in the world switch and let it be
+	 * handled by kvm_timer_sync_from_cpu(). Getting a timer
+	 * interrupt at this point is a sure sign of some major
+	 * breakage.
+	 */
+	pr_warn("Unexpected interrupt %d on vcpu %p\n", irq, vcpu);
+	return IRQ_HANDLED;
+}
+
+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);
+	vcpu->arch.timer_cpu.armed = false;
+	kvm_timer_inject_irq(vcpu);
+}
+
+static enum hrtimer_restart kvm_timer_expire(struct hrtimer *hrt)
+{
+	struct arch_timer_cpu *timer;
+	timer = container_of(hrt, struct arch_timer_cpu, timer);
+	queue_work(wqueue, &timer->expired);
+	return HRTIMER_NORESTART;
+}
+
+void kvm_timer_sync_to_cpu(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	/*
+	 * We're about to run this vcpu again, so there is no need to
+	 * keep the background timer running, as we're about to
+	 * populate the CPU timer again.
+	 */
+	if (timer->armed) {
+		hrtimer_cancel(&timer->timer);
+		cancel_work_sync(&timer->expired);
+		timer->armed = false;
+	}
+}
+
+void kvm_timer_sync_from_cpu(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+	cycle_t cval, now;
+	u64 ns;
+
+	/* Check if the timer is enabled and unmasked first */
+	if ((timer->cntv_ctl & 3) != 1)
+		return;
+
+	cval = timer->cntv_cval;
+	now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
+
+	BUG_ON(timer->armed);
+
+	if (cval <= now) {
+		/*
+		 * Timer has already expired while we were not
+		 * looking. Inject the interrupt and carry on.
+		 */
+		kvm_timer_inject_irq(vcpu);
+		return;
+	}
+
+	timer->armed = true;
+	ns = cyclecounter_cyc2ns(timecounter->cc, cval - now);
+	hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
+		      HRTIMER_MODE_ABS);
+}
+
+void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	INIT_WORK(&timer->expired, kvm_timer_inject_irq_work);
+	hrtimer_init(&timer->timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	timer->timer.function = kvm_timer_expire;
+}
+
+static void kvm_timer_init_interrupt(void *info)
+{
+	unsigned int *irqp = info;
+
+	enable_percpu_irq(*irqp, 0);
+}
+
+
+static const struct of_device_id arch_timer_of_match[] = {
+	{ .compatible	= "arm,armv7-timer",	},
+	{},
+};
+
+int kvm_timer_hyp_init(void)
+{
+	struct device_node *np;
+	unsigned int ppi;
+	int err;
+
+	timecounter = arch_timer_get_timecounter();
+	if (!timecounter)
+		return -ENODEV;
+
+	np = of_find_matching_node(NULL, arch_timer_of_match);
+	if (!np) {
+		kvm_err("kvm_arch_timer: can't find DT node\n");
+		return -ENODEV;
+	}
+
+	ppi = irq_of_parse_and_map(np, 2);
+	if (!ppi) {
+		kvm_err("kvm_arch_timer: no virtual timer interrupt\n");
+		return -EINVAL;
+	}
+
+	err = request_percpu_irq(ppi, kvm_arch_timer_handler,
+				 "kvm guest timer", kvm_get_running_vcpus());
+	if (err) {
+		kvm_err("kvm_arch_timer: can't request interrupt %d (%d)\n",
+			ppi, err);
+		return err;
+	}
+
+	wqueue = create_singlethread_workqueue("kvm_arch_timer");
+	if (!wqueue) {
+		free_percpu_irq(ppi, kvm_get_running_vcpus());
+		return -ENOMEM;
+	}
+
+	kvm_info("%s IRQ%d\n", np->name, ppi);
+	on_each_cpu(kvm_timer_init_interrupt, &ppi, 1);
+
+	return 0;
+}
+
+void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	hrtimer_cancel(&timer->timer);
+	cancel_work_sync(&timer->expired);
+}
+
+int kvm_timer_init(struct kvm *kvm)
+{
+	if (timecounter && wqueue) {
+		kvm->arch.timer.cntvoff = kvm_phys_timer_read();
+		kvm->arch.timer.enabled = 1;
+	}
+
+	return 0;
+}