On Mon, Dec 15, 2014 at 10:39:23AM +0000, Marc Zyngier wrote: > On 15/12/14 10:20, Christoffer Dall wrote: > > It is curently possible to run a VM with architected timers support > > without creating an in-kernel VGIC, which will result in interrupts from > > the virtual timer going nowhere. > > > > To address this issue, move the architected timers initialization to the > > time when we run a VCPU for the first time, and then only initialize > > (and enable) the architected timers if we have a properly created and > > initialized in-kernel VGIC. > > > > When injecting interrupts from the virtual timer to the vgic, the > > current setup should ensure that this never calls an on-demand init of > > the VGIC, which is the only call path that could return an error from > > kvm_vgic_inject_irq(), so capture the return value and raise a warning > > if there's an error there. > > > > We also change the kvm_timer_init() function from returning an int to be > > a void function, since the function always succeeds. > > > > Signed-off-by: Christoffer Dall <christoffer.dall@xxxxxxxxxx> > > --- > > Changes [v2 -> v3]: > > - Split kvm_timer_init into kvm_timer_init and kvm_timer_enable > > and initialize the cntvoff in kvm_timer_init and only actually enable > > the timer if there is an in-kernel vgic. > > - Added comment about race from multiple VCPUs. > > - Support compiling on 32-bit ARM wihtout vgic/arch-timers config > > option. > > > > arch/arm/kvm/arm.c | 13 +++++++++++-- > > include/kvm/arm_arch_timer.h | 10 ++++------ > > virt/kvm/arm/arch_timer.c | 30 ++++++++++++++++++++++-------- > > 3 files changed, 37 insertions(+), 16 deletions(-) > > > > diff --git a/arch/arm/kvm/arm.c b/arch/arm/kvm/arm.c > > index d4da244..8cadfec 100644 > > --- a/arch/arm/kvm/arm.c > > +++ b/arch/arm/kvm/arm.c > > @@ -424,6 +424,7 @@ static void update_vttbr(struct kvm *kvm) > > > > static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) > > { > > + struct kvm *kvm = vcpu->kvm; > > int ret; > > > > if (likely(vcpu->arch.has_run_once)) > > @@ -435,12 +436,20 @@ static int kvm_vcpu_first_run_init(struct kvm_vcpu *vcpu) > > * Map the VGIC hardware resources before running a vcpu the first > > * time on this VM. > > */ > > - if (unlikely(!vgic_ready(vcpu->kvm))) { > > - ret = kvm_vgic_map_resources(vcpu->kvm); > > + if (unlikely(!vgic_ready(kvm))) { > > + ret = kvm_vgic_map_resources(kvm); > > if (ret) > > return ret; > > } > > > > + /* > > + * Enable the arch timers only if we have an in-kernel VGIC > > + * and it has been properly initialized, since we cannot handle > > + * interrupts from the virtual timer with a userspace gic. > > + */ > > + if (irqchip_in_kernel(kvm) && vgic_initialized(kvm)) > > + kvm_timer_enable(kvm); > > + > > return 0; > > } > > > > diff --git a/include/kvm/arm_arch_timer.h b/include/kvm/arm_arch_timer.h > > index ad9db60..b3f45a5 100644 > > --- a/include/kvm/arm_arch_timer.h > > +++ b/include/kvm/arm_arch_timer.h > > @@ -60,7 +60,8 @@ struct arch_timer_cpu { > > > > #ifdef CONFIG_KVM_ARM_TIMER > > int kvm_timer_hyp_init(void); > > -int kvm_timer_init(struct kvm *kvm); > > +void kvm_timer_enable(struct kvm *kvm); > > +void kvm_timer_init(struct kvm *kvm); > > void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu, > > const struct kvm_irq_level *irq); > > void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu); > > @@ -77,11 +78,8 @@ 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_enable(struct kvm *kvm) {} > > +static inline void kvm_timer_init(struct kvm *kvm) {} > > static inline void kvm_timer_vcpu_reset(struct kvm_vcpu *vcpu, > > const struct kvm_irq_level *irq) {} > > static inline void kvm_timer_vcpu_init(struct kvm_vcpu *vcpu) {} > > diff --git a/virt/kvm/arm/arch_timer.c b/virt/kvm/arm/arch_timer.c > > index 22fa819..1c0772b 100644 > > --- a/virt/kvm/arm/arch_timer.c > > +++ b/virt/kvm/arm/arch_timer.c > > @@ -61,12 +61,14 @@ static void timer_disarm(struct arch_timer_cpu *timer) > > > > static void kvm_timer_inject_irq(struct kvm_vcpu *vcpu) > > { > > + int ret; > > struct arch_timer_cpu *timer = &vcpu->arch.timer_cpu; > > > > timer->cntv_ctl |= ARCH_TIMER_CTRL_IT_MASK; > > - kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id, > > - timer->irq->irq, > > - timer->irq->level); > > + ret = kvm_vgic_inject_irq(vcpu->kvm, vcpu->vcpu_id, > > + timer->irq->irq, > > + timer->irq->level); > > + WARN_ON(ret); > > } > > > > static irqreturn_t kvm_arch_timer_handler(int irq, void *dev_id) > > @@ -307,12 +309,24 @@ void kvm_timer_vcpu_terminate(struct kvm_vcpu *vcpu) > > timer_disarm(timer); > > } > > > > -int kvm_timer_init(struct kvm *kvm) > > +void kvm_timer_enable(struct kvm *kvm) > > { > > - if (timecounter && wqueue) { > > - kvm->arch.timer.cntvoff = kvm_phys_timer_read(); > > + if (kvm->arch.timer.enabled) > > + return; > > + > > + /* > > + * There is a potential race here between VCPUs starting for the first > > + * time, which may be enabling the timer multiple times. That doesn't > > + * hurt though, because we're just setting a variable to the same > > + * variable that it already was. The important thing is that all > > + * VCPUs have the enabled variable set, before entering the guest, if > > + * the arch timers are enabled. > > + */ > > + if (timecounter && wqueue) > > kvm->arch.timer.enabled = 1; > > - } > > +} > > This is particularly interesting, as this paves the way for per-vcpu > enable bits, meaning that we won't have to extract the enable bit from > struct kvm while doing a world switch. Clearly a fight for another day > though. > I didn't think of that, but sounds good. > > > > - return 0; > > +void kvm_timer_init(struct kvm *kvm) > > +{ > > + kvm->arch.timer.cntvoff = kvm_phys_timer_read(); > > } > > > > Looks good to me. > > Reviewed-by: Marc Zyngier <marc.zyngier@xxxxxxx> > Thanks, I'll go ahead and get these series merged then. -Christoffer -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html