Re: [PATCH] nVMX: Fix warning-causing idt-vectoring-info behavior

[Avi Kivity <avi@redhat.com>]

On 09/21/2011 01:48 PM, Nadav Har'El wrote:
> This patch solves two outstanding nested-VMX issues:

<snip>

Sorry, I missed an important point on the first review.

> --- .before/arch/x86/kvm/vmx.c	2011-09-21 13:45:59.000000000 +0300
> +++ .after/arch/x86/kvm/vmx.c	2011-09-21 13:45:59.000000000 +0300
> @@ -3858,12 +3858,17 @@ static bool nested_exit_on_intr(struct k
>   static void enable_irq_window(struct kvm_vcpu *vcpu)
>   {
>   	u32 cpu_based_vm_exec_control;
> -	if (is_guest_mode(vcpu)&&  nested_exit_on_intr(vcpu))
> -		/* We can get here when nested_run_pending caused
> -		 * vmx_interrupt_allowed() to return false. In this case, do
> -		 * nothing - the interrupt will be injected later.
> +	if (is_guest_mode(vcpu)&&  nested_exit_on_intr(vcpu)) {
> +		/*
> +		 * We get here if vmx_interrupt_allowed() returned 0 because
> +		 * we must enter L2 now, so we can't inject to L1 now. If we
> +		 * just do nothing, L2 will later exit and we can inject the
> +		 * IRQ to L1 then. But to make L2 exit more promptly, we send
> +		 * a self-IPI, causing L2 to exit right after entry.
>   		 */
> +		smp_send_reschedule(vcpu->cpu);
>   		return;
> +	}

->enable_irq_window() is called with interrupts enabled, so the self-IPI 
will be dispatched immediately and be lost.

The way to handle it is to kvm_make_request(KVM_REQ_IMMEDIATE_EXIT) 
here, and to add code to vcpu_enter_guest() to sample this into a local 
variable, and, after disabling interrupts, do the self-IPI.

A unit test would have caught this...

-- 
error compiling committee.c: too many arguments to function