Re: [PATCH v2 3/3] KVM: Non-atomic interrupt injection

[Avi Kivity]

On 07/21/2010 03:55 AM, Marcelo Tosatti wrote:

--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -4709,6 +4709,19 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
        if (unlikely(r))
                goto out;

+       inject_pending_event(vcpu);
+
+       /* enable NMI/IRQ window open exits if needed */
+       if (vcpu->arch.nmi_pending)
+               kvm_x86_ops->enable_nmi_window(vcpu);
+       else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
+               kvm_x86_ops->enable_irq_window(vcpu);
+
+       if (kvm_lapic_enabled(vcpu)) {
+               update_cr8_intercept(vcpu);
+               kvm_lapic_sync_to_vapic(vcpu);
+       }
+
        preempt_disable();

        kvm_x86_ops->prepare_guest_switch(vcpu);
@@ -4727,23 +4740,11 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
                smp_wmb();
                local_irq_enable();
                preempt_enable();
+               kvm_x86_ops->cancel_injection(vcpu);
                r = 1;
                goto out;
        }

-       inject_pending_event(vcpu);
-
-       /* enable NMI/IRQ window open exits if needed */
-       if (vcpu->arch.nmi_pending)
-               kvm_x86_ops->enable_nmi_window(vcpu);
-       else if (kvm_cpu_has_interrupt(vcpu) || req_int_win)
-               kvm_x86_ops->enable_irq_window(vcpu);
-
-       if (kvm_lapic_enabled(vcpu)) {
-               update_cr8_intercept(vcpu);
-               kvm_lapic_sync_to_vapic(vcpu);
-       }
-
        srcu_read_unlock(&vcpu->kvm->srcu, vcpu->srcu_idx);

        kvm_guest_enter();

This breaks

int kvm_lapic_find_highest_irr(struct kvm_vcpu *vcpu)
{
         struct kvm_lapic *apic = vcpu->arch.apic;
         int highest_irr;

         /* This may race with setting of irr in __apic_accept_irq() and
          * value returned may be wrong, but kvm_vcpu_kick() in
          * __apic_accept_irq
          * will cause vmexit immediately and the value will be
          * recalculated
          * on the next vmentry.
          */

(also valid for nmi_pending and PIC). Can't simply move
atomic_set(guest_mode, 1) in preemptible section as that would make it
possible for kvm_vcpu_kick to IPI stale vcpu->cpu.

Right.  Can fix by adding a kvm_make_request() to force the retry loop.

Also should undo vmx.rmode.* ?

Elaborate?

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.

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