On Fri, 2022-06-17 at 20:35 +0530, Shukla, Santosh wrote:
>
> On 6/7/2022 6:44 PM, Maxim Levitsky wrote:
> > On Thu, 2022-06-02 at 19:56 +0530, Santosh Shukla wrote:
> > > Inject the NMI by setting V_NMI in the VMCB interrupt control. processor
> > > will clear V_NMI to acknowledge processing has started and will keep the
> > > V_NMI_MASK set until the processor is done with processing the NMI event.
> > >
> > > Signed-off-by: Santosh Shukla <santosh.shukla@xxxxxxx>
> > > ---
> > > arch/x86/kvm/svm/svm.c | 7 ++++++-
> > > 1 file changed, 6 insertions(+), 1 deletion(-)
> > >
> > > diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
> > > index a405e414cae4..200f979169e0 100644
> > > --- a/arch/x86/kvm/svm/svm.c
> > > +++ b/arch/x86/kvm/svm/svm.c
> > > @@ -3385,11 +3385,16 @@ static void svm_inject_nmi(struct kvm_vcpu *vcpu)
> > > {
> > > struct vcpu_svm *svm = to_svm(vcpu);
> > >
> > > + ++vcpu->stat.nmi_injections;
> > > + if (is_vnmi_enabled(svm->vmcb)) {
> > > + svm->vmcb->control.int_ctl |= V_NMI_PENDING;
> > > + return;
> > > + }
> > Here I would advice to have a warning to check if vNMI is already pending.
> >
> Yes, in v2.
>
> > Also we need to check what happens if we make vNMI pending and get #SMI,
> > while in #NMI handler, or if #NMI is blocked due to interrupt window.
> >
>
> V_NMI_MASK should be saved as 1 in the save area and
> hypervisor will resume the NMI handler after handling the SMI.
Answering my own question, because I did some homework in this area while
working on that SMI int shadow bug:
Actually what will happen (now I checked) is that we have a special KVM host state flag
(called X86EMUL_SMM_MASK, and HF_SMM_INSIDE_NMI_MASK), and what we do is that if we
receive SMI while in NMI handler, we don't mask the NMI again, on RSM we don't unmask NMI.
Also, as I found out the hard way recently, the NMI is not blocked by the interrupt shadow.
I don't think that anything is saved to the SMRAM in this case.
Best regards,
Maxim Levitsky
>
> Thanks,
> Santosh
>
> > Best regards,
> > Maxim Levitsky
> >
> >
> > > +
> > > svm->vmcb->control.event_inj = SVM_EVTINJ_VALID | SVM_EVTINJ_TYPE_NMI;
> > > vcpu->arch.hflags |= HF_NMI_MASK;
> > > if (!sev_es_guest(vcpu->kvm))
> > > svm_set_intercept(svm, INTERCEPT_IRET);
> > > - ++vcpu->stat.nmi_injections;
> > > }
> > >
> > > static void svm_inject_irq(struct kvm_vcpu *vcpu)
