Re: [PATCH v3 1/4] KVM: nVMX: Rework interception of IRQs and NMIs

[Paolo Bonzini <pbonzini@redhat.com>]

Il 08/03/2014 10:21, Jan Kiszka ha scritto:
> On 2014-03-07 20:48, Paolo Bonzini wrote:
>> Il 07/03/2014 20:03, Jan Kiszka ha scritto:
>>> @@ -4631,22 +4631,8 @@ static void vmx_set_nmi_mask(struct kvm_vcpu
>>> *vcpu, bool masked)
>>>
>>>  static int vmx_nmi_allowed(struct kvm_vcpu *vcpu)
>>>  {
>>> -    if (is_guest_mode(vcpu)) {
>>> -        if (to_vmx(vcpu)->nested.nested_run_pending)
>>> -            return 0;
>>> -        if (nested_exit_on_nmi(vcpu)) {
>>> -            nested_vmx_vmexit(vcpu, EXIT_REASON_EXCEPTION_NMI,
>>> -                      NMI_VECTOR | INTR_TYPE_NMI_INTR |
>>> -                      INTR_INFO_VALID_MASK, 0);
>>> -            /*
>>> -             * The NMI-triggered VM exit counts as injection:
>>> -             * clear this one and block further NMIs.
>>> -             */
>>> -            vcpu->arch.nmi_pending = 0;
>>> -            vmx_set_nmi_mask(vcpu, true);
>>> -            return 0;
>>> -        }
>>> -    }
>>> +    if (to_vmx(vcpu)->nested.nested_run_pending)
>>> +        return 0;
>>>
>>>      if (!cpu_has_virtual_nmis() && to_vmx(vcpu)->soft_vnmi_blocked)
>>>          return 0;
>>> @@ -4658,19 +4644,8 @@ static int vmx_nmi_allowed(struct kvm_vcpu *vcpu)
>>>
>>>  static int vmx_interrupt_allowed(struct kvm_vcpu *vcpu)
>>>  {
>>> -    if (is_guest_mode(vcpu)) {
>>> -        if (to_vmx(vcpu)->nested.nested_run_pending)
>>> -            return 0;
>>> -        if (nested_exit_on_intr(vcpu)) {
>>> -            nested_vmx_vmexit(vcpu, EXIT_REASON_EXTERNAL_INTERRUPT,
>>> -                      0, 0);
>>> -            /*
>>> -             * fall through to normal code, but now in L1, not L2
>>> -             */
>>> -        }
>>> -    }
>>> -
>>> -    return (vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) &&
>>> +    return (!to_vmx(vcpu)->nested.nested_run_pending &&
>>> +        vmcs_readl(GUEST_RFLAGS) & X86_EFLAGS_IF) &&
>>>          !(vmcs_read32(GUEST_INTERRUPTIBILITY_INFO) &
>>>              (GUEST_INTR_STATE_STI | GUEST_INTR_STATE_MOV_SS));
>>
>> The checks on nested_run_pending are not needed anymore and can be
>> replaced with a WARN_ON.  Otherwise,
>
> Nope, that won't be correct: If we have a pending interrupt that L1 does
> not intercept, we still trigger this condition legally.

Right, this is the case of !nested_exit_on_intr(vcpu) or 
!nested_exit_on_nmi(vcpu).

Why don't we need to request an immediate exit in that case, in order to 
inject the interrupt into L2?

Paolo