On Thu, 2021-11-04 at 19:26 +0000, Sean Christopherson wrote:
> On Wed, Nov 03, 2021, Maxim Levitsky wrote:
> > KVM_GUESTDBG_BLOCKIRQ relies on interrupts being injected using
> > standard kvm's inject_pending_event, and not via APICv/AVIC.
> >
> > Since this is a debug feature, just inhibit APICv/AVIC while
> > KVM_GUESTDBG_BLOCKIRQ is in use on at least one vCPU.
>
> Very clever!
Thanks! It is now possible to enjoy this,
after we broke our back making APICv/AVIC inhibition actually work...
>
> > Fixes: 61e5f69ef0837 ("KVM: x86: implement KVM_GUESTDBG_BLOCKIRQ")
> >
> > Signed-off-by: Maxim Levitsky <mlevitsk@xxxxxxxxxx>
> > ---
>
> With the below nits resolved (tested on Intel w/ APICv):
>
> Reviewed-and-tested-by: Sean Christopherson <seanjc@xxxxxxxxxx>
>
> > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
> > index ac83d873d65b0..5d30cea58182e 100644
> > --- a/arch/x86/kvm/x86.c
> > +++ b/arch/x86/kvm/x86.c
> > @@ -10703,6 +10703,25 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu,
> > return ret;
> > }
> >
> > +static void kvm_arch_vcpu_guestdbg_update_apicv_inhibit(struct kvm *kvm)
> > +{
> > + struct kvm_vcpu *vcpu = NULL;
>
> vcpu doesn't need to be initialized.
True, fixed in v4
>
> > + int i;
>
> Nit, I'd prefer we use reverse fir tree when it's convenient, i.e.
Fixed in v4
>
> bool block_irq_used = false;
> struct kvm_vcpu *vcpu;
> int i;
>
> > + bool block_irq_used = false;
> > +
> > + down_write(&kvm->arch.apicv_update_lock);
> > +
> > + kvm_for_each_vcpu(i, vcpu, kvm) {
> > + if (vcpu->guest_debug & KVM_GUESTDBG_BLOCKIRQ) {
> > + block_irq_used = true;
> > + break;
> > + }
> > + }
> > + __kvm_request_apicv_update(kvm, !block_irq_used,
> > + APICV_INHIBIT_REASON_BLOCKIRQ);
>
> Heh, this indentation is still messed up, I think you need to change your
>
> if (r == -ENOCOFFEE)
> maxim_get_coffee();
>
> to
>
> while (r == -ENOCOFFEE)
> r = maxim_get_coffee();
Yep :-)
>
> > + up_write(&kvm->arch.apicv_update_lock);
> > +}
> > +
> > int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> > struct kvm_guest_debug *dbg)
> > {
> > @@ -10755,6 +10774,8 @@ int kvm_arch_vcpu_ioctl_set_guest_debug(struct kvm_vcpu *vcpu,
> >
> > static_call(kvm_x86_update_exception_bitmap)(vcpu);
> >
> > + kvm_arch_vcpu_guestdbg_update_apicv_inhibit(vcpu->kvm);
> > +
> > r = 0;
> >
> > out:
> > --
> > 2.26.3
> >
Thanks for the review,
Best regards,
Maxim Levitsky
