Re: [PATCH v5 04/20] KVM: arm/arm64: Guard kvm_vgic_map_is_active against !vgic_initialized

Andre Przywara
2017-11-16T12:29:48Z

Hi,

On 27/10/17 09:34, Christoffer Dall wrote:
> If the vgic is not initialized, don't try to grab its spinlocks or
> traverse its data structures.
>
> This is important because we soon have to start considering the active
> state of a virtual interrupts when doing vcpu_load, which may happen
> early on before the vgic is initialized.

I understand this patch is on its way to Linus already, but I just found
this by browsing for VGIC changes...

> Signed-off-by: Christoffer Dall <cdall@linaro.org>
> Acked-by: Marc Zyngier <marc.zyngier@arm.com>
> ---
> virt/kvm/arm/vgic/vgic.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/virt/kvm/arm/vgic/vgic.c b/virt/kvm/arm/vgic/vgic.c
> index fed717e..e1f7dbc 100644
> --- a/virt/kvm/arm/vgic/vgic.c
> +++ b/virt/kvm/arm/vgic/vgic.c
> @@ -777,6 +777,9 @@ bool kvm_vgic_map_is_active(struct kvm_vcpu *vcpu, unsigned int virt_irq)
> struct vgic_irq *irq = vgic_get_irq(vcpu->kvm, vcpu, virt_irq);

Isn't vgic_get_irq() already accessing VGIC data structures? In which
case this assignment should be moved after the vgic_initialized() check
below?

Cheers,
Andre.

> bool map_is_active;
>
> + if (!vgic_initialized(vcpu->kvm))
> + return false;
> +
> spin_lock(&irq->irq_lock);
> map_is_active = irq->hw && irq->active;
> spin_unlock(&irq->irq_lock);
>