Re: [PATCH v2] KVM: x86: Account for failing enable_irq_window for NMI window request

[Paolo Bonzini <pbonzini@redhat.com>]

Il 29/04/2013 16:46, Jan Kiszka ha scritto:
> With VMX, enable_irq_window can now return -EBUSY, in which case an
> immediate exit shall be requested before entering the guest. Account for
> this also in enable_nmi_window which uses enable_irq_window in absence
> of vnmi support, e.g.
> 
> Signed-off-by: Jan Kiszka <jan.kiszka@siemens.com>

Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>

> ---
> 
> Changes in v2:
>  - check return code of enable_nmi_window against 0 instead of using it
>    directly
> 
>  arch/x86/include/asm/kvm_host.h |    2 +-
>  arch/x86/kvm/svm.c              |    5 +++--
>  arch/x86/kvm/vmx.c              |   16 +++++++---------
>  arch/x86/kvm/x86.c              |    3 ++-
>  4 files changed, 13 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
> index ec14b72..3741c65 100644
> --- a/arch/x86/include/asm/kvm_host.h
> +++ b/arch/x86/include/asm/kvm_host.h
> @@ -695,7 +695,7 @@ struct kvm_x86_ops {
>  	int (*nmi_allowed)(struct kvm_vcpu *vcpu);
>  	bool (*get_nmi_mask)(struct kvm_vcpu *vcpu);
>  	void (*set_nmi_mask)(struct kvm_vcpu *vcpu, bool masked);
> -	void (*enable_nmi_window)(struct kvm_vcpu *vcpu);
> +	int (*enable_nmi_window)(struct kvm_vcpu *vcpu);
>  	int (*enable_irq_window)(struct kvm_vcpu *vcpu);
>  	void (*update_cr8_intercept)(struct kvm_vcpu *vcpu, int tpr, int irr);
>  	int (*vm_has_apicv)(struct kvm *kvm);
> diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
> index 7f896cb..3421d5a 100644
> --- a/arch/x86/kvm/svm.c
> +++ b/arch/x86/kvm/svm.c
> @@ -3649,13 +3649,13 @@ static int enable_irq_window(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> -static void enable_nmi_window(struct kvm_vcpu *vcpu)
> +static int enable_nmi_window(struct kvm_vcpu *vcpu)
>  {
>  	struct vcpu_svm *svm = to_svm(vcpu);
>  
>  	if ((svm->vcpu.arch.hflags & (HF_NMI_MASK | HF_IRET_MASK))
>  	    == HF_NMI_MASK)
> -		return; /* IRET will cause a vm exit */
> +		return 0; /* IRET will cause a vm exit */
>  
>  	/*
>  	 * Something prevents NMI from been injected. Single step over possible
> @@ -3664,6 +3664,7 @@ static void enable_nmi_window(struct kvm_vcpu *vcpu)
>  	svm->nmi_singlestep = true;
>  	svm->vmcb->save.rflags |= (X86_EFLAGS_TF | X86_EFLAGS_RF);
>  	update_db_bp_intercept(vcpu);
> +	return 0;
>  }
>  
>  static int svm_set_tss_addr(struct kvm *kvm, unsigned int addr)
> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
> index 55a1aa0..2f7af9c 100644
> --- a/arch/x86/kvm/vmx.c
> +++ b/arch/x86/kvm/vmx.c
> @@ -4417,22 +4417,20 @@ static int enable_irq_window(struct kvm_vcpu *vcpu)
>  	return 0;
>  }
>  
> -static void enable_nmi_window(struct kvm_vcpu *vcpu)
> +static int enable_nmi_window(struct kvm_vcpu *vcpu)
>  {
>  	u32 cpu_based_vm_exec_control;
>  
> -	if (!cpu_has_virtual_nmis()) {
> -		enable_irq_window(vcpu);
> -		return;
> -	}
> +	if (!cpu_has_virtual_nmis())
> +		return enable_irq_window(vcpu);
> +
> +	if (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_STI)
> +		return enable_irq_window(vcpu);
>  
> -	if (vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) & GUEST_INTR_STATE_STI) {
> -		enable_irq_window(vcpu);
> -		return;
> -	}
>  	cpu_based_vm_exec_control = vmcs_read32(CPU_BASED_VM_EXEC_CONTROL);
>  	cpu_based_vm_exec_control |= CPU_BASED_VIRTUAL_NMI_PENDING;
>  	vmcs_write32(CPU_BASED_VM_EXEC_CONTROL, cpu_based_vm_exec_control);
> +	return 0;
>  }
>  
>  static void vmx_inject_irq(struct kvm_vcpu *vcpu)
> diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> index 8747fef..24724b42 100644
> --- a/arch/x86/kvm/x86.c
> +++ b/arch/x86/kvm/x86.c
> @@ -5754,7 +5754,8 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
>  
>  		/* enable NMI/IRQ window open exits if needed */
>  		if (vcpu->arch.nmi_pending)
> -			kvm_x86_ops->enable_nmi_window(vcpu);
> +			req_immediate_exit =
> +				kvm_x86_ops->enable_nmi_window(vcpu) != 0;
>  		else if (kvm_cpu_has_injectable_intr(vcpu) || req_int_win)
>  			req_immediate_exit =
>  				kvm_x86_ops->enable_irq_window(vcpu) != 0;
>