Re: [PATCH] KVM: arm/arm64: don't set vtimer->cnt_ctl in kvm_arch_timer_handler

[Christoffer Dall]

On Fri, Dec 15, 2017 at 10:27:02AM +0800, Jia He wrote:

[...]

> >diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c
> >index 73d262c4712b..544ed15fbbb3 100644
> >--- a/virt/kvm/arm/arch_timer.c
> >+++ b/virt/kvm/arm/arch_timer.c
> >@@ -46,7 +46,7 @@ static const struct kvm_irq_level default_vtimer_irq = {
> >  	.level	= 1,
> >  };
> >-static bool kvm_timer_irq_can_fire(struct arch_timer_context *timer_ctx);
> >+static bool kvm_timer_irq_can_fire(u32 cnt_ctl);
> >  static void kvm_timer_update_irq(struct kvm_vcpu *vcpu, bool new_level,
> >  				 struct arch_timer_context *timer_ctx);
> >  static bool kvm_timer_should_fire(struct arch_timer_context *timer_ctx);
> >@@ -94,6 +94,7 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
> >  {
> >  	struct kvm_vcpu *vcpu = *(struct kvm_vcpu **)dev_id;
> >  	struct arch_timer_context *vtimer;
> >+	u32 cnt_ctl;
> >  	if (!vcpu) {
> >  		pr_warn_once("Spurious arch timer IRQ on non-VCPU thread\n");
> >@@ -101,8 +102,8 @@ static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id)
> >  	}
> >  	vtimer = vcpu_vtimer(vcpu);
> >-	vtimer->cnt_ctl = read_sysreg_el0(cntv_ctl);
> >-	if (kvm_timer_irq_can_fire(vtimer))
> >+	cnt_ctl = read_sysreg_el0(cntv_ctl);
> >+	if (kvm_timer_irq_can_fire(cnt_ctl))
> >  		kvm_timer_update_irq(vcpu, true, vtimer);
> IIUC, your patch makes kvm_arch_timer_handler never changesvtimer->cnt_ctl

Yes, that's the idea.

Meanwhile, I think I thought of a cleaner way to do this.  Could you
test the following two patches on your platform as well?