linux-kernel - [PATCH RT 06/30] KVM: arm/arm64: Let the timer expire in hardirq context on RT

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Date:   Thu, 23 Jan 2020 15:39:36 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     linux-kernel@...r.kernel.org,
        linux-rt-users <linux-rt-users@...r.kernel.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Carsten Emde <C.Emde@...dl.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        John Kacur <jkacur@...hat.com>,
        Julia Cartwright <julia@...com>,
        Daniel Wagner <wagi@...om.org>,
        Tom Zanussi <zanussi@...nel.org>,
        Marc Zyngier <maz@...nel.org>,
        Julien Grall <julien.grall@....com>
Subject: [PATCH RT 06/30] KVM: arm/arm64: Let the timer expire in hardirq context on RT

4.19.94-rt39-rc2 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Thomas Gleixner <tglx@...utronix.de>

[ Upstream commit 719cc080c914045a6e35787bf4dc3ba91cfd3efb ]

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@...utronix.de>
Acked-by: Marc Zyngier <maz@...nel.org>
Tested-by: Julien Grall <julien.grall@....com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Signed-off-by: Steven Rostedt (VMware) <rostedt@...dmis.org>
---
 virt/kvm/arm/arch_timer.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
index 17cecc96f735..217d39f40393 100644
--- a/virt/kvm/arm/arch_timer.c
+++ b/virt/kvm/arm/arch_timer.c
@@ -67,7 +67,7 @@ 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, struct work_struct *work)
@@ -638,10 +638,10 @@ void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu)
 	vcpu_ptimer(vcpu)->cntvoff = 0;
 
 	INIT_WORK(&timer->expired, kvm_timer_inject_irq_work);
-	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(&timer->phys_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
+	hrtimer_init(&timer->phys_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
 	timer->phys_timer.function = kvm_phys_timer_expire;
 
 	vtimer->irq.irq = default_vtimer_irq.irq;
-- 
2.24.1