| Message ID | 20211009021236.4122790-21-seanjc@google.com |
|---|---|
| State | New |
| Headers | show |
| Series | KVM: Halt-polling and x86 APICv overhaul | expand |
On 09/10/21 04:12, Sean Christopherson wrote: > + /* Nothing to do if PI.SN==0 and the vCPU isn't being migrated. */ > if (!pi_test_sn(pi_desc) && vcpu->cpu == cpu) > return; This does not quite say "why", so: /* Nothing to do if PI.SN and PI.NDST both have the desired value. */ Paolo
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 <seanjc@google.com> > --- > 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 <mlevitsk@redhat.com> Best regards, Maxim Levitsky
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;
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 <seanjc@google.com> --- arch/x86/kvm/vmx/posted_intr.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-)