ARM: KVM: arch_timers: Add guest timer core support

Add some the architected timer related infrastructure, and support timer
interrupt injection, which can happen as a resultof 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
Reviewed-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Christoffer Dall <c.dall@virtualopensystems.com>
Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>

arch/arm/include/asm/kvm_arch_timer.h

+/*
+ * 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
+ */
+
+#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 */
+	cycle_t			cntvoff;
+#endif
+};
+
+struct arch_timer_cpu {
+#ifdef CONFIG_KVM_ARM_TIMER
+	/* Registers: control register, timer value */
+	u32				cntv_ctl;	/* Saved/restored */
+	cycle_t				cntv_cval;	/* Saved/restored */
+
+	/*
+	 * Anything that is not used directly from assembly code goes
+	 * here.
+	 */
+
+	/* 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;
+#endif
+};
+
+#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_flush_hwstate(struct kvm_vcpu *vcpu);
+void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu);
+void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu);
+#else
+static inline int kvm_timer_hyp_init(void)
+{
+	return 0;
+};
+
+static inline int kvm_timer_init(struct kvm *kvm)
+{
+	return 0;
+}
+
+static inline void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) {}
+static inline void kvm_timer_flush_hwstate(struct kvm_vcpu *vcpu) {}
+static inline void kvm_timer_sync_hwstate(struct kvm_vcpu *vcpu) {}
+static inline void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu) {}
+#endif
+
+#endif

arch/arm/include/asm/kvm_host.h

@@ -23,6 +23,7 @@
 #include <asm/kvm_asm.h>
 #include <asm/kvm_mmio.h>
 #include <asm/fpstate.h>
+#include <asm/kvm_arch_timer.h>
 
 #define KVM_MAX_VCPUS CONFIG_KVM_ARM_MAX_VCPUS
 #define KVM_MEMORY_SLOTS 32
@@ -49,6 +50,9 @@ struct kvm_arch {
 	/* VTTBR value associated with below pgd and vmid */
 	u64    vttbr;
 
+	/* Timer */
+	struct arch_timer_kvm	timer;
+
 	/*
 	 * Anything that is not used directly from assembly code goes
 	 * here.
@@ -99,6 +103,7 @@ struct kvm_vcpu_arch {
 
 	/* VGIC state */
 	struct vgic_cpu vgic_cpu;
+	struct arch_timer_cpu timer_cpu;
 
 	/*
 	 * Anything that is not used directly from assembly code goes

arch/arm/kvm/arch_timer.c

+/*
+ * 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/cpu.h>
+#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 struct kvm_irq_level timer_irq = {
+	.level	= 1,
+};
+
+static cycle_t kvm_phys_timer_read(void)
+{
+	return timecounter->cc->read(timecounter->cc);
+}
+
+static bool timer_is_armed(struct arch_timer_cpu *timer)
+{
+	return timer->armed;
+}
+
+/* timer_arm: as in "arm the timer", not as in ARM the company */
+static void timer_arm(struct arch_timer_cpu *timer, u64 ns)
+{
+	timer->armed = true;
+	hrtimer_start(&timer->timer, ktime_add_ns(ktime_get(), ns),
+		      HRTIMER_MODE_ABS);
+}
+
+static void timer_disarm(struct arch_timer_cpu *timer)
+{
+	if (timer_is_armed(timer)) {
+		hrtimer_cancel(&timer->timer);
+		cancel_work_sync(&timer->expired);
+		timer->armed = false;
+	}
+}
+
+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_hwstate(). 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;
+}
+
+/**
+ * kvm_timer_flush_hwstate - prepare to move the virt timer to the cpu
+ * @vcpu: The vcpu pointer
+ *
+ * Disarm any pending soft timers, since the world-switch code will write the
+ * virtual timer state back to the physical CPU.
+ */
+void kvm_timer_flush_hwstate(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.
+	 */
+	timer_disarm(timer);
+}
+
+/**
+ * kvm_timer_sync_hwstate - sync timer state from cpu
+ * @vcpu: The vcpu pointer
+ *
+ * Check if the virtual timer was armed and either schedule a corresponding
+ * soft timer or inject directly if already expired.
+ */
+void kvm_timer_sync_hwstate(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_is_armed(timer));
+
+	if (cval <= now) {
+		/*
+		 * Timer has already expired while we were not
+		 * looking. Inject the interrupt and carry on.
+		 */
+		kvm_timer_inject_irq(vcpu);
+		return;
+	}
+
+	ns = cyclecounter_cyc2ns(timecounter->cc, cval - now);
+	timer_arm(timer, ns);
+}
+
+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;
+	timer->irq = &timer_irq;
+}
+
+static void kvm_timer_init_interrupt(void *info)
+{
+	enable_percpu_irq(timer_irq.irq, 0);
+}
+
+
+static int kvm_timer_cpu_notify(struct notifier_block *self,
+				unsigned long action, void *cpu)
+{
+	switch (action) {
+	case CPU_STARTING:
+	case CPU_STARTING_FROZEN:
+		kvm_timer_init_interrupt(NULL);
+		break;
+	case CPU_DYING:
+	case CPU_DYING_FROZEN:
+		disable_percpu_irq(timer_irq.irq);
+		break;
+	}
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block kvm_timer_cpu_nb = {
+	.notifier_call = kvm_timer_cpu_notify,
+};
+
+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");
+		err = -EINVAL;
+		goto out;
+	}
+
+	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);
+		goto out;
+	}
+
+	timer_irq.irq = ppi;
+
+	err = register_cpu_notifier(&kvm_timer_cpu_nb);
+	if (err) {
+		kvm_err("Cannot register timer CPU notifier\n");
+		goto out_free;
+	}
+
+	wqueue = create_singlethread_workqueue("kvm_arch_timer");
+	if (!wqueue) {
+		err = -ENOMEM;
+		goto out_free;
+	}
+
+	kvm_info("%s IRQ%d\n", np->name, ppi);
+	on_each_cpu(kvm_timer_init_interrupt, NULL, 1);
+
+	goto out;
+out_free:
+	free_percpu_irq(ppi, kvm_get_running_vcpus());
+out:
+	of_node_put(np);
+	return err;
+}
+
+void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu)
+{
+	struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu;
+
+	timer_disarm(timer);
+}
+
+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;
+}

arch/arm/kvm/interrupts.S

@@ -95,6 +95,7 @@ ENTRY(__kvm_vcpu_run)
 	save_host_regs
 
 	restore_vgic_state
+	restore_timer_state
 
 	@ Store hardware CP15 state and load guest state
 	read_cp15_state store_to_vcpu = 0
@@ -189,6 +190,7 @@ after_vfp_restore:
 	read_cp15_state store_to_vcpu = 1
 	write_cp15_state read_from_vcpu = 0
 
+	save_timer_state
 	save_vgic_state
 
 	restore_host_regs

arch/arm/kvm/interrupts_head.S

@@ -453,6 +453,37 @@ vcpu	.req	r0		@ vcpu pointer always in r0
 #endif
 .endm
 
+#define CNTHCTL_PL1PCTEN	(1 << 0)
+#define CNTHCTL_PL1PCEN		(1 << 1)
+
+/*
+ * Save the timer state onto the VCPU and allow physical timer/counter access
+ * for the host.
+ *
+ * Assumes vcpu pointer in vcpu reg
+ */
+.macro save_timer_state
+	@ Allow physical timer/counter access for the host
+	mrc	p15, 4, r2, c14, c1, 0	@ CNTHCTL
+	orr	r2, r2, #(CNTHCTL_PL1PCEN | CNTHCTL_PL1PCTEN)
+	mcr	p15, 4, r2, c14, c1, 0	@ CNTHCTL
+.endm
+
+/*
+ * Load the timer state from the VCPU and deny physical timer/counter access
+ * for the host.
+ *
+ * Assumes vcpu pointer in vcpu reg
+ */
+.macro restore_timer_state
+	@ Disallow physical timer access for the guest
+	@ Physical counter access is allowed
+	mrc	p15, 4, r2, c14, c1, 0	@ CNTHCTL
+	orr	r2, r2, #CNTHCTL_PL1PCTEN
+	bic	r2, r2, #CNTHCTL_PL1PCEN
+	mcr	p15, 4, r2, c14, c1, 0	@ CNTHCTL
+.endm
+
 .equ vmentry,	0
 .equ vmexit,	1