Re: [PATCH 5/5] arm/arm64: KVM: Initialize the vgic on-demand when injecting IRQs

Marc Zyngier
2014-12-11T18:35:53Z

On 09/12/14 15:44, Christoffer Dall wrote:
> Userspace assumes that it can wire up IRQ injections after having
> created all VCPUs and after having created the VGIC, but potentially
> before starting the first VCPU. This can currently lead to lost IRQs
> because the state of that IRQ injection is not stored anywhere and we
> don't return an error to userspace.
>
> We haven't seen this problem manifest itself yet, presumably because
> guests reset the devices on boot, but this could cause issues with
> migration and other non-standard startup configurations.
>
> Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
> ---
> virt/kvm/arm/vgic.c | 9 +++++++--
> 1 file changed, 7 insertions(+), 2 deletions(-)
>
> diff --git a/virt/kvm/arm/vgic.c b/virt/kvm/arm/vgic.c
> index c98cc6b..feef015 100644
> --- a/virt/kvm/arm/vgic.c
> +++ b/virt/kvm/arm/vgic.c
> @@ -1693,8 +1693,13 @@ out:
> int kvm_vgic_inject_irq(struct kvm *kvm, int cpuid, unsigned int irq_num,
> bool level)
> {
> - if (likely(vgic_ready(kvm)) &&
> - vgic_update_irq_pending(kvm, cpuid, irq_num, level))
> + if (unlikely(!vgic_initialized(kvm))) {
> + mutex_lock(&kvm->lock);
> + vgic_init(kvm);

What if this fails?

> + mutex_unlock(&kvm->lock);
> + }
> +
> + if (vgic_update_irq_pending(kvm, cpuid, irq_num, level))
> vgic_kick_vcpus(kvm);
>
> return 0;
>

M.
--
Jazz is not dead. It just smells funny...