[PATCH 2/3] KVM: x86: forward LAPIC ICR writes to userspace

[muliang.shou]

Intercept LAPIC ICR/ICR2 MMIO writes, record the forwarding payload, and
return to userspace with KVM_EXIT_DSM_SEND_IRQ when the pending request is
processed.

Signed-off-by: muliang.shou <muliang.shou@xxxxxxxxxxx>
---
 arch/x86/kvm/lapic.c | 30 ++++++++++++++++++++++++++++++
 arch/x86/kvm/x86.c   | 14 ++++++++++++++
 2 files changed, 44 insertions(+)

diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 4078e624ca667..2485d50b45647 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -2561,6 +2561,10 @@ static int apic_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this,
 	struct kvm_lapic *apic = to_lapic(this);
 	unsigned int offset = address - apic->base_address;
 	u32 val;
+#ifdef CONFIG_KVM_DSM_IRQ_FORWARD
+	u32 reg;
+	u32 dest_id = 0;
+#endif
 
 	if (!apic_mmio_in_range(apic, address))
 		return -EOPNOTSUPP;
@@ -2583,6 +2587,32 @@ static int apic_mmio_write(struct kvm_vcpu *vcpu, struct kvm_io_device *this,
 
 	val = *(u32*)data;
 
+#ifdef CONFIG_KVM_DSM_IRQ_FORWARD
+	reg = offset & 0xff0;
+	if (reg == APIC_ICR || reg == APIC_ICR2) {
+		kvm_lapic_reg_write(apic, reg, val);
+		if (reg == APIC_ICR) {
+			if (apic_x2apic_mode(apic)) {
+				dest_id = kvm_lapic_get_reg(apic, APIC_ICR2);
+			} else {
+				dest_id = kvm_lapic_get_reg(apic, APIC_ICR2);
+				dest_id = GET_XAPIC_DEST_FIELD(dest_id);
+			}
+		} else {
+			dest_id = GET_XAPIC_DEST_FIELD(val);
+		}
+
+		vcpu->arch.dsm_irq_forward_pending = true;
+		vcpu->arch.dsm_irq_forward_reg = reg;
+		vcpu->arch.dsm_irq_forward_val = val;
+		vcpu->arch.dsm_irq_forward_dest_id = dest_id;
+
+		kvm_make_request(KVM_REQ_DSM_IRQ_FORWARD, vcpu);
+
+		return 0;
+	}
+#endif
+
 	kvm_lapic_reg_write(apic, offset & 0xff0, val);
 
 	return 0;
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index 0550359ed798f..42d6f8c977985 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -11338,6 +11338,20 @@ static int vcpu_enter_guest(struct kvm_vcpu *vcpu)
 				goto out;
 			}
 		}
+#ifdef CONFIG_KVM_DSM_IRQ_FORWARD
+		if (kvm_check_request(KVM_REQ_DSM_IRQ_FORWARD, vcpu)) {
+			vcpu->run->exit_reason = KVM_EXIT_DSM_SEND_IRQ;
+			vcpu->run->lapic_irq.id = vcpu->vcpu_id;
+			vcpu->run->lapic_irq.val = vcpu->arch.dsm_irq_forward_reg;
+			vcpu->run->lapic_irq.val2 = vcpu->arch.dsm_irq_forward_val;
+			vcpu->run->lapic_irq.dest_id = vcpu->arch.dsm_irq_forward_dest_id;
+
+			vcpu->arch.dsm_irq_forward_pending = false;
+
+			r = 0;
+			goto out;
+		}
+#endif
 	}
 
 	if (kvm_check_request(KVM_REQ_EVENT, vcpu) || req_int_win ||
-- 
2.43.0