Re: kernel device reset support

[Avi Kivity <avi-atKUWr5tajBWk0Htik3J/w@public.gmane.org>]

Dong, Eddie wrote:
> Kernel side patch to introduce a new API for kernel device reset and
> force
> vcpu mp_state to UNINATIALIZED state if it is reset.
> thx,eddie
>
>
>
> +
> +/*
> + * Reset VM.
> + *
> + */
> +int kvm_vm_reset(struct kvm *kvm)
> +{
> +	struct kvm_vcpu *vcpu;
> +	int i;
> +
> +	kvm_reset_devices(kvm);
> +	for (i = 0; i < KVM_MAX_VCPUS; i++) {
> +		vcpu = kvm->vcpus[i];
> +		if (!vcpu)
> +			continue;
> +		/* active VCPU */
> +		if (vcpu->vcpu_id)
> +			vcpu->mp_state = VCPU_MP_STATE_UNINITIALIZED;
> +		else {
> +			vcpu->mp_state = VCPU_MP_STATE_RUNNABLE;
> +			kvm_lapic_reset(vcpu);
>   

Why is the handling here different?

> +		}
> +		vcpu->force_to_quit = 1;
> +		kvm_vcpu_kick(vcpu);
> +	}
> +	return 0;
> +}
> +
>  static long kvm_vm_ioctl(struct file *filp,
>  			   unsigned int ioctl, unsigned long arg)
>  {
> @@ -3163,6 +3200,12 @@ static long kvm_vm_ioctl(struct file *filp,
>  		else
>  			goto out;
>  		break;
> +	case KVM_RESET:
> +		r = -EFAULT;
>   

-EINVAL.  Or better accept it always and only reset the vcpu if
!irqchip_in_kernel().

> +		if (!irqchip_in_kernel(kvm))
> +			goto out;
> +		r = kvm_vm_reset(kvm);
> +		break;
>  	case KVM_IRQ_LINE: {
>  		struct kvm_irq_level irq_event;
>  
> diff --git a/drivers/kvm/vmx.c b/drivers/kvm/vmx.c
> index 3d8e01e..0799aad 100644
> --- a/drivers/kvm/vmx.c
> +++ b/drivers/kvm/vmx.c
> @@ -1860,6 +1860,10 @@ static int handle_external_interrupt(struct
> kvm_vcpu *vcpu,
>  				     struct kvm_run *kvm_run)
>  {
>  	++vcpu->stat.irq_exits;
> +	if (vcpu->force_to_quit) {
> +		vcpu->force_to_quit = 0;
> +		return -EINTR;
> +	}
>  	return 1;
>  }
>   

Why is this needed?

Userspace can always force an exit by sending a signal.

-- 
Do not meddle in the internals of kernels, for they are subtle and quick to panic.


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