> -----Original Message----- > From: Paolo Bonzini [mailto:paolo.bonzini@xxxxxxxxx] On Behalf Of Paolo > Bonzini > Sent: Wednesday, September 28, 2016 5:20 AM > To: linux-kernel@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx > Cc: yang.zhang.wz@xxxxxxxxx; Wu, Feng <feng.wu@xxxxxxxxx>; > mst@xxxxxxxxxx; rkrcmar@xxxxxxxxxx > Subject: [PATCH 2/3] kvm: x86: do not use KVM_REQ_EVENT for APICv interrupt > injection > > Since bf9f6ac8d749 ("KVM: Update Posted-Interrupts Descriptor when vCPU > is blocked", 2015-09-18) the posted interrupt descriptor is checked > unconditionally for PIR.ON. Therefore we don't need KVM_REQ_EVENT to > trigger the scan and, if NMIs or SMIs are not involved, we can avoid > the complicated event injection path. But the following code still remains in the KVM_REQ_EVENT checking part: if (kvm_lapic_enabled(vcpu)) { update_cr8_intercept(vcpu); kvm_lapic_sync_to_vapic(vcpu); } Does this matter? Thanks, Feng > > However, there is a race between vmx_deliver_posted_interrupt and > vcpu_enter_guest. Fix it by disabling interrupts before vcpu->mode is > set to IN_GUEST_MODE. > > Calling kvm_vcpu_kick if PIR.ON=1 is also useless, though it has been > there since APICv was introduced. > > Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx> > --- > arch/x86/kvm/lapic.c | 2 -- > arch/x86/kvm/vmx.c | 8 +++++--- > arch/x86/kvm/x86.c | 9 +++++++-- > 3 files changed, 12 insertions(+), 7 deletions(-) > > diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c > index 63a442aefc12..be8b7ad56dd1 100644 > --- a/arch/x86/kvm/lapic.c > +++ b/arch/x86/kvm/lapic.c > @@ -356,8 +356,6 @@ void kvm_apic_update_irr(struct kvm_vcpu *vcpu, u32 > *pir) > struct kvm_lapic *apic = vcpu->arch.apic; > > __kvm_apic_update_irr(pir, apic->regs); > - > - kvm_make_request(KVM_REQ_EVENT, vcpu); > } > EXPORT_SYMBOL_GPL(kvm_apic_update_irr); > > diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c > index b33eee395b00..207b9aa32915 100644 > --- a/arch/x86/kvm/vmx.c > +++ b/arch/x86/kvm/vmx.c > @@ -4844,9 +4844,11 @@ static void vmx_deliver_posted_interrupt(struct > kvm_vcpu *vcpu, int vector) > if (pi_test_and_set_pir(vector, &vmx->pi_desc)) > return; > > - r = pi_test_and_set_on(&vmx->pi_desc); > - kvm_make_request(KVM_REQ_EVENT, vcpu); > - if (r || !kvm_vcpu_trigger_posted_interrupt(vcpu)) > + /* If a previous notification has sent the IPI, nothing to do. */ > + if (pi_test_and_set_on(&vmx->pi_desc)) > + return; > + > + if (!kvm_vcpu_trigger_posted_interrupt(vcpu)) > kvm_vcpu_kick(vcpu); > } > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index 3ee8a91a78c3..604cfbfc5bee 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -6658,6 +6658,13 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) > kvm_x86_ops->prepare_guest_switch(vcpu); > if (vcpu->fpu_active) > kvm_load_guest_fpu(vcpu); > + > + /* > + * Disable IRQs before setting IN_GUEST_MODE, so that > + * posted interrupts with vcpu->mode == IN_GUEST_MODE > + * always result in virtual interrupt delivery. > + */ > + local_irq_disable(); > vcpu->mode = IN_GUEST_MODE; > > srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx); > @@ -6671,8 +6678,6 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu) > */ > smp_mb__after_srcu_read_unlock(); > > - local_irq_disable(); > - > if (vcpu->mode == EXITING_GUEST_MODE || vcpu->requests > || need_resched() || signal_pending(current)) { > vcpu->mode = OUTSIDE_GUEST_MODE; > -- > 1.8.3.1 > -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
