Hi Sebastian,
On 8/13/19 1:58 PM, bigeasy@xxxxxxxxxxxxx wrote:
On 2019-07-27 14:37:11 [+0100], Julien Grall wrote:
8<------------
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -80,7 +80,7 @@ static inline bool userspace_irqchip(str
static void soft_timer_start(struct hrtimer *hrt, u64 ns)
{
hrtimer_start(hrt, ktime_add_ns(ktime_get(), ns),
- HRTIMER_MODE_ABS);
+ HRTIMER_MODE_ABS_HARD);
}
That's pretty neat, and matches the patch you already have for
x86. Feel free to add my
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
I can confirm the warning now disappeared. Feel free to added my tested-by:
Tested-by: Julien Grall <julien.grall@xxxxxxx>
|kvm_hrtimer_expire()
| kvm_timer_update_irq()
| kvm_vgic_inject_irq()
| vgic_lazy_init()
| if (unlikely(!vgic_initialized(kvm))) {
| if (kvm->arch.vgic.vgic_model != KVM_DEV_TYPE_ARM_VGIC_V2)
| return -EBUSY;
|
| mutex_lock(&kvm->lock);
Is this possible path of any concern? This should throw a warning also
for !RT so probably not…
Hmmm, theoretically yes. In practice, it looks like the hrtimer will not
be started before kvm_vcpu_first_run_init() is called on the first run.
The function will call kvm_vgic_map_resources() which will initialize
the vgic if not already done.
Looking around, I think this is here to cater the case where
KVM_IRQ_LINE is called before running.
I am not yet familiar with the vgic, so I may have missed something.
I prepared the patch below. This one could go straight to tglx's timer tree
since he has the _HARD bits there. I *think* it requires to set the bits
_HARD during _init() and _start() otherwise there is (or was) a warning…
Sebastian
8<------------
From: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Date: Tue, 13 Aug 2019 14:29:41 +0200
Subject: [PATCH] KVM: arm/arm64: Let the timer expire in hardirq context on RT
The timers are canceled from an preempt-notifier which is invoked with
disabled preemption which is not allowed on PREEMPT_RT.
The timer callback is short so in could be invoked in hard-IRQ context
on -RT.
Let the timer expire on hard-IRQ context even on -RT.
Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Acked-by: Marc Zyngier <maz@xxxxxxxxxx>
Tested-by: Julien Grall <julien.grall@xxxxxxx>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
virt/kvm/arm/arch_timer.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)
diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 1be486d5d7cb4..0bfa7c5b5c890 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -80,7 +80,7 @@ static inline bool userspace_irqchip(struct kvm *kvm)
static void soft_timer_start(struct hrtimer *hrt, u64 ns)
{
hrtimer_start(hrt, ktime_add_ns(ktime_get(), ns),
- HRTIMER_MODE_ABS);
+ HRTIMER_MODE_ABS_HARD);
}
static void soft_timer_cancel(struct hrtimer *hrt)
@@ -697,11 +697,11 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
update_vtimer_cntvoff(vcpu, kvm_phys_timer_read());
ptimer->cntvoff = 0;
- hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+ hrtimer_init(&timer->bg_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
timer->bg_timer.function = kvm_bg_timer_expire;
- hrtimer_init(&vtimer->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
- hrtimer_init(&ptimer->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+ hrtimer_init(&vtimer->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
+ hrtimer_init(&ptimer->hrtimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
vtimer->hrtimer.function = kvm_hrtimer_expire;
ptimer->hrtimer.function = kvm_hrtimer_expire;
--
Julien Grall
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