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    SubjectRe: [PATCH v2 07/11] KVM: x86: add a delayed hardware NMI injection interface
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    On Sat, 2023-01-28 at 01:09 +0000, Sean Christopherson wrote:
    > On Tue, Nov 29, 2022, Maxim Levitsky wrote:
    > > This patch adds two new vendor callbacks:
    >
    > No "this patch" please, just say what it does.
    >
    > > diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
    > > index 684a5519812fb2..46993ce61c92db 100644
    > > --- a/arch/x86/include/asm/kvm_host.h
    > > +++ b/arch/x86/include/asm/kvm_host.h
    > > @@ -871,8 +871,13 @@ struct kvm_vcpu_arch {
    > > u64 tsc_scaling_ratio; /* current scaling ratio */
    > >
    > > atomic_t nmi_queued; /* unprocessed asynchronous NMIs */
    > > - unsigned nmi_pending; /* NMI queued after currently running handler */
    > > +
    > > + unsigned int nmi_pending; /*
    > > + * NMI queued after currently running handler
    > > + * (not including a hardware pending NMI (e.g vNMI))
    > > + */
    >
    > Put the block comment above. I'd say collapse all of the comments about NMIs into
    > a single big block comment.
    >
    > > bool nmi_injected; /* Trying to inject an NMI this entry */
    > > +
    > > bool smi_pending; /* SMI queued after currently running handler */
    > > u8 handling_intr_from_guest;
    > >
    > > @@ -10015,13 +10022,34 @@ static void process_nmi(struct kvm_vcpu *vcpu)
    > > * Otherwise, allow two (and we'll inject the first one immediately).
    > > */
    > > if (static_call(kvm_x86_get_nmi_mask)(vcpu) || vcpu->arch.nmi_injected)
    > > - limit = 1;
    > > + limit--;
    > > +
    > > + /* Also if there is already a NMI hardware queued to be injected,
    > > + * decrease the limit again
    > > + */
    >
    > /*
    > * Block comment ...
    > */
    >
    > > + if (static_call(kvm_x86_get_hw_nmi_pending)(vcpu))
    >
    > I'd prefer "is_hw_nmi_pending()" over "get", even if it means not pairing with
    > "set". Though I think that's a good thing since they aren't perfect pairs.
    >
    > > + limit--;
    > >
    > > - vcpu->arch.nmi_pending += atomic_xchg(&vcpu->arch.nmi_queued, 0);
    > > + if (limit <= 0)
    > > + return;
    > > +
    > > + /* Attempt to use hardware NMI queueing */
    > > + if (static_call(kvm_x86_set_hw_nmi_pending)(vcpu)) {
    > > + limit--;
    > > + nmi_to_queue--;
    > > + }
    > > +
    > > + vcpu->arch.nmi_pending += nmi_to_queue;
    > > vcpu->arch.nmi_pending = min(vcpu->arch.nmi_pending, limit);
    > > kvm_make_request(KVM_REQ_EVENT, vcpu);
    > > }
    > >
    > > +/* Return total number of NMIs pending injection to the VM */
    > > +int kvm_get_total_nmi_pending(struct kvm_vcpu *vcpu)
    > > +{
    > > + return vcpu->arch.nmi_pending + static_call(kvm_x86_get_hw_nmi_pending)(vcpu);
    >
    > Nothing cares about the total count, this can just be;

    I wanted to have the interface to be a bit more generic so that in theory you could have
    more that one hardware NMI pending. I don't care much about it.


    Best regards,
    Maxim Levitsky

    >
    >
    > bool kvm_is_nmi_pending(struct kvm_vcpu *vcpu)
    > {
    > return vcpu->arch.nmi_pending ||
    > static_call(kvm_x86_is_hw_nmi_pending)(vcpu);
    > }
    >
    >
    > > +}
    > > +
    > > void kvm_make_scan_ioapic_request_mask(struct kvm *kvm,
    > > unsigned long *vcpu_bitmap)
    > > {
    > > --
    > > 2.26.3
    > >


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