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

[Jan Kiszka <jan.kiszka@web.de>]

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On 2014-03-09 08:33, Paolo Bonzini wrote:
> 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?

We enable the hardware interrupt/NMI window request for L2 instead.

Jan



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