Re: [PATCH] KVM: x86: Check KVM_REQ_IMMEDIATE_EXIT after enable_irq_window

[Gleb Natapov <gleb@redhat.com>]

On Sun, Apr 28, 2013 at 09:23:58AM +0200, Jan Kiszka wrote:
> From: Jan Kiszka <jan.kiszka@siemens.com>
> 
> The VMX implementation of enable_irq_window will raise
> KVM_REQ_IMMEDIATE_EXIT if an interrupt window shall be opened during
> nested vmrun. We have to transfer this request into the local variable
> to avoid looping over a continuously re-asserted request on vmentry.
> 
> This issue only affects nested VMX scenarios.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>
So KVM_REQ_IMMEDIATE_EXIT does not behave like request bit should. What
about dropping it and letting enable_irq_window() return true if
immediate exit is needed.

> ---
>  arch/x86/kvm/x86.c |    3 +++
>  1 files changed, 3 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 2a434bf..57ff14a 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5759,6 +5759,9 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  		else if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win)
>  			kvm_x86_ops->enable_irq_window(vcpu);
>  
> +		req_immediate_exit =
> +			kvm_check_request(KVM_REQ_IMMEDIATE_EXIT, vcpu);
> +
The code will become:
   req_immediate_exit = kvm_x86_ops->enable_irq_window(vcpu);

>  		if (kvm_lapic_enabled(vcpu)) {
>  			/*
>  			 * Update architecture specific hints for APIC
> -- 
> 1.7.3.4

--
			Gleb.