Andrea Arcangeli wrote:
> On Wed, Aug 13, 2008 at 10:05:06AM +0200, Jan Kiszka wrote:
>> Should this issue have been fixed meanwhile? I just gave latest git a
>> try and - as far as I recall my tests before holiday correctly - things
>> look the same. At least some Linux 2.6.23 kernel still hangs here during
>> early boot with -no-kvm-irqchip.
> 
> The trouble was that clearing the idt_vectoring_info before handling
> the exit_reason would lead to the handle_exception to fail setting the
> irq_pending bit because is_external_interrupt was run on zero instead
> of the vmcs IDT_VECTORING_INFO_FIELD, so it didn't notice it was an
> external interrupt generating the exit.
> 
> This makes the userland irqchip code work again for me, there seem to
> be no good reason to clear this value before returning in guest mode
> and only setting it to zero didn't look an effective debugging aid, so
> it's a microoptimization for the kernel irqchip too.
> 
> Signed-off-by: Andrea Arcangeli <andrea@qumranet.com>

Solves the issue here as well. Thanks.

Tested-by: Jan Kiszka <jan.kiszka@web.de>

> 
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 337670b..3c82593 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -2890,13 +2890,10 @@ static void vmx_complete_interrupts(struct vcpu_vmx *vmx)
>  			kvm_queue_exception_e(&vmx->vcpu, vector, error);
>  		} else
>  			kvm_queue_exception(&vmx->vcpu, vector);
> -		vmx->idt_vectoring_info = 0;
>  	}
>  	kvm_clear_interrupt_queue(&vmx->vcpu);
> -	if (idtv_info_valid && type == INTR_TYPE_EXT_INTR) {
> +	if (idtv_info_valid && type == INTR_TYPE_EXT_INTR)
>  		kvm_queue_interrupt(&vmx->vcpu, vector);
> -		vmx->idt_vectoring_info = 0;
> -	}
>  }
>  
>  static void vmx_intr_assist(struct kvm_vcpu *vcpu)
>