KVM: x86: Add KVM exit for IOAPIC EOIs
Adds KVM_EXIT_IOAPIC_EOI which allows the kernel to EOI
level-triggered IOAPIC interrupts.
Uses a per VCPU exit bitmap to decide whether or not the IOAPIC needs
to be informed (which is identical to the EOI_EXIT_BITMAP field used
by modern x86 processors, but can also be used to elide kvm IOAPIC EOI
exits on older processors).
[Note: A prototype using ResampleFDs found that decoupling the EOI
from the VCPU's thread made it possible for the VCPU to not see a
recent EOI after reentering the guest. This does not match real
hardware.]
Compile tested for Intel x86.
Signed-off-by: Steve Rutherford <srutherford@google.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index e05946c3..ef70f6f 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -877,15 +877,25 @@
static void kvm_ioapic_send_eoi(struct kvm_lapic *apic, int vector)
{
- if (kvm_ioapic_handles_vector(apic, vector)) {
- int trigger_mode;
- if (apic_test_vector(vector, apic->regs + APIC_TMR))
- trigger_mode = IOAPIC_LEVEL_TRIG;
- else
- trigger_mode = IOAPIC_EDGE_TRIG;
+ int trigger_mode;
- kvm_ioapic_update_eoi(apic->vcpu, vector, trigger_mode);
+ /* Eoi the ioapic only if the ioapic doesn't own the vector. */
+ if (!kvm_ioapic_handles_vector(apic, vector))
+ return;
+
+ /* Request a KVM exit to inform the userspace IOAPIC. */
+ if (irqchip_split(apic->vcpu->kvm)) {
+ apic->vcpu->arch.pending_ioapic_eoi = vector;
+ kvm_make_request(KVM_REQ_IOAPIC_EOI_EXIT, apic->vcpu);
+ return;
}
+
+ if (apic_test_vector(vector, apic->regs + APIC_TMR))
+ trigger_mode = IOAPIC_LEVEL_TRIG;
+ else
+ trigger_mode = IOAPIC_EDGE_TRIG;
+
+ kvm_ioapic_update_eoi(apic->vcpu, vector, trigger_mode);
}
static int apic_set_eoi(struct kvm_lapic *apic)