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!
> 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.
> + int i;
Nit, I'd prefer we use reverse fir tree when it's convenient, i.e.
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();
> + 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
>
