[PATCH v4 3/5] ARM: KVM: arch_timers: Add guest timer core support
Will Deacon
will.deacon at arm.com
Fri Nov 23 11:17:59 EST 2012
On Sat, Nov 10, 2012 at 03:46:19PM +0000, Christoffer Dall wrote:
> From: Marc Zyngier <marc.zyngier at 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 at arm.com>
> Signed-off-by: Christoffer Dall <c.dall at virtualopensystems.com>
> ---
> arch/arm/include/asm/kvm_arch_timer.h | 57 +++++++++
> arch/arm/kvm/reset.c | 9 +
> arch/arm/kvm/timer.c | 204 +++++++++++++++++++++++++++++++++
> 3 files changed, 269 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..bd5e501 100644
> --- a/arch/arm/include/asm/kvm_arch_timer.h
> +++ b/arch/arm/include/asm/kvm_arch_timer.h
> @@ -19,13 +19,68 @@
> #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
Endianness?
> };
>
> struct arch_timer_cpu {
> +#ifdef CONFIG_KVM_ARM_TIMER
> + /* 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;
> + };
Similarly.
> + /*
> + * 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
> };
>
> -#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 b80256b..7463f5b 100644
> --- a/arch/arm/kvm/reset.c
> +++ b/arch/arm/kvm/reset.c
> @@ -37,6 +37,12 @@ static struct kvm_regs a15_regs_reset = {
> .usr_regs.ARM_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 }, /* irq: A7/A15 specific */
This should be parameterised by the vCPU type.
> + .level = 1 /* level */
> +};
> +#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
Maybe kvm/arch_timer.c since it seems to be specific to that device and
matches the naming for the main driver under kernel/? If we get new virtual
timer devices in the future, I guess this would need to be split up so the
arch-timer-specific bits are separate from generic hrtimer and kvm code.
> @@ -0,0 +1,204 @@
> +/*
> + * Copyright (C) 2012 ARM Ltd.
> + * Author: Marc Zyngier <marc.zyngier at 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 */
This is ARCH_TIMER_CTRL_IT_MASK right? We should make that definition
available if it is needed here.
> + 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;
IRQ_NONE?
> +}
> +
> +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;
> + }
> +}
I think some helper functions like timer_is_armed, timer_arm and
timer_disarm would make this more readable (resisting arm_timer, which
confuses things more!).
> +
> +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;
Again, we should create/use ARCH_TIMER #defines for this hardware bits.
> + cval = timer->cntv_cval;
> + now = kvm_phys_timer_read() - vcpu->kvm->arch.timer.cntvoff;
We probably want to add an isb() *before* the mrrc in
arch_timer_counter_read if you want to do things like this, because the
counter can be speculated in advance.
> + 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;
> + }
Does this buy you much? You still have to cope with the timer expiring here
anyway.
> + 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);
IRQ_TYPE_NONE
> +}
> +
> +
> +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);
on_each_cpu currently just returns 0, but you could use that as your return
value for good measure anyway.
> + 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();
Shouldn't this be initialised to 0 and then updated on world switch?
Will
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