On Fri, 2021-10-08 at 19:12 -0700, Sean Christopherson wrote:
> Explicitly skip posted interrupt updates if APICv is disabled in all of
> KVM, or if the guest doesn't have an in-kernel APIC. The PI descriptor
> is kept up-to-date if APICv is inhibited, e.g. so that re-enabling APICv
> doesn't require a bunch of updates, but neither the module param nor the
> APIC type can be changed on-the-fly.
>
> Signed-off-by: Sean Christopherson <[email protected]>
> ---
> arch/x86/kvm/vmx/posted_intr.c | 11 +++++++----
> 1 file changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/arch/x86/kvm/vmx/posted_intr.c b/arch/x86/kvm/vmx/posted_intr.c
> index 3263056784f5..351666c41bbc 100644
> --- a/arch/x86/kvm/vmx/posted_intr.c
> +++ b/arch/x86/kvm/vmx/posted_intr.c
> @@ -28,11 +28,14 @@ void vmx_vcpu_pi_load(struct kvm_vcpu *vcpu, int cpu)
> unsigned int dest;
>
> /*
> - * In case of hot-plug or hot-unplug, we may have to undo
> - * vmx_vcpu_pi_put even if there is no assigned device. And we
> - * always keep PI.NDST up to date for simplicity: it makes the
> - * code easier, and CPU migration is not a fast path.
> + * To simplify hot-plug and dynamic toggling of APICv, keep PI.NDST and
> + * PI.SN up-to-date even if there is no assigned device or if APICv is
> + * deactivated due to a dynamic inhibit bit, e.g. for Hyper-V's SyncIC.
> */
> + if (!enable_apicv || !lapic_in_kernel(vcpu))
> + return;
> +
> + /* Nothing to do if PI.SN==0 and the vCPU isn't being migrated. */
> if (!pi_test_sn(pi_desc) && vcpu->cpu == cpu)
> return;
>
Reviewed-by: Maxim Levitsky <[email protected]>
Best regards,
Maxim Levitsky
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