linux-kernel - Re: [PATCH 2/6] kvm: nVMX: move nested events check to kvm_vcpu

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Message-ID: <20170207181559.GB31091@potion>
Date:   Tue, 7 Feb 2017 19:16:00 +0100
From:   Radim Krčmář <rkrcmar@...hat.com>
To:     Paolo Bonzini <pbonzini@...hat.com>
Cc:     linux-kernel@...r.kernel.org, kvm@...r.kernel.org
Subject: Re: [PATCH 2/6] kvm: nVMX: move nested events check to
 kvm_vcpu_running

2016-12-19 17:17+0100, Paolo Bonzini:
> vcpu_run calls kvm_vcpu_running, not kvm_arch_vcpu_runnable,
> and the former does not call check_nested_events.
> 
> Once KVM_REQ_EVENT is removed from the APICv interrupt injection
> path, however, this would leave no place to trigger a vmexit
> from L2 to L1, causing a missed interrupt delivery while in guest
> mode.  This is caught by the "ack interrupt on exit" test in
> vmx.flat.
> 
> [This does not change the calls to check_nested_events in
>  inject_pending_event.  That is material for a separate cleanup.]
> 
> Signed-off-by: Paolo Bonzini <pbonzini@...hat.com>
> ---

I think we should now remove the call to check_nested_events() from
inject_pending_event() and we could also call it in vcpu_enter_guest()
directly.

Still,

Reviewed-by: Radim Krčmář <rkrcmar@...hat.com

>  arch/x86/kvm/x86.c | 6 +++---
>  1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index d5a5fc2f8758..32e5f54a8eba 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -6920,6 +6920,9 @@ static inline int vcpu_block(struct kvm *kvm, struct kvm_vcpu *vcpu)
>  
>  static inline bool kvm_vcpu_running(struct kvm_vcpu *vcpu)
>  {
> +	if (is_guest_mode(vcpu) && kvm_x86_ops->check_nested_events)
> +		kvm_x86_ops->check_nested_events(vcpu, false);
> +
>  	return (vcpu->arch.mp_state == KVM_MP_STATE_RUNNABLE &&
>  		!vcpu->arch.apf.halted);
>  }
> @@ -8286,9 +8289,6 @@ static inline bool kvm_vcpu_has_events(struct kvm_vcpu *vcpu)
>  
>  int kvm_arch_vcpu_runnable(struct kvm_vcpu *vcpu)
>  {
> -	if (is_guest_mode(vcpu) && kvm_x86_ops->check_nested_events)
> -		kvm_x86_ops->check_nested_events(vcpu, false);
> -
>  	return kvm_vcpu_running(vcpu) || kvm_vcpu_has_events(vcpu);
>  }
>  
> -- 
> 1.8.3.1
> 
> 
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