[RFC PATCH 5/9] KVM: SVM: Bypass lapic for VMPL1-3 guest with Alternate Injection enabled

[Melody Wang <huibo.wang@amd.com>]

The interrupts for VMPL1-3 are handled in the SVSM by its APIC emulation
so bypass the KVM's APIC layer and queue them into the doorbell page.

Signed-off-by: Melody Wang <huibo.wang@amd.com>
---
 arch/x86/include/asm/kvm-x86-ops.h | 1 +
 arch/x86/include/asm/kvm_host.h    | 1 +
 arch/x86/kvm/lapic.c               | 7 +++++--
 arch/x86/kvm/svm/svm.c             | 6 ++++++
 4 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
index 16da6d1678e5..dfd38f9408cc 100644
--- a/arch/x86/include/asm/kvm-x86-ops.h
+++ b/arch/x86/include/asm/kvm-x86-ops.h
@@ -96,6 +96,7 @@ KVM_X86_OP_OPTIONAL_RET0(set_tss_addr)
 KVM_X86_OP_OPTIONAL_RET0(set_identity_map_addr)
 KVM_X86_OP_OPTIONAL_RET0(get_mt_mask)
 KVM_X86_OP_OPTIONAL_RET0(has_interrupt)
+KVM_X86_OP_OPTIONAL_RET0(is_bypass_apic_active)
 KVM_X86_OP(load_mmu_pgd)
 KVM_X86_OP_OPTIONAL(link_external_spt)
 KVM_X86_OP_OPTIONAL(set_external_spte)
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 985d7f4d7140..60c102db1003 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -1874,6 +1874,7 @@ struct kvm_x86_ops {
 	void (*patch_hypercall)(struct kvm_vcpu *vcpu,
 				unsigned char *hypercall_addr);
 	int (*has_interrupt)(struct kvm_vcpu *vcpu);
+	bool (*is_bypass_apic_active)(struct kvm_vcpu *vcpu);
 	void (*inject_irq)(struct kvm_vcpu *vcpu, bool reinjected);
 	void (*inject_nmi)(struct kvm_vcpu *vcpu);
 	void (*inject_exception)(struct kvm_vcpu *vcpu);
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index 9ebae1052f64..952b6cc92ede 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -3189,8 +3189,11 @@ void kvm_apic_ack_interrupt(struct kvm_vcpu *vcpu, int vector)
 		 * a concurrent interrupt injection, but that would have
 		 * triggered KVM_REQ_EVENT already.
 		 */
-		apic_set_isr(vector, apic);
-		__apic_update_ppr(apic, &ppr);
+		if (!kvm_x86_call(is_bypass_apic_active)(vcpu)) {
+			apic_set_isr(vector, apic);
+			__apic_update_ppr(apic, &ppr);
+		}
+
 	}
 
 }
diff --git a/arch/x86/kvm/svm/svm.c b/arch/x86/kvm/svm/svm.c
index 7c4b3d05ae88..756b11bebb5a 100644
--- a/arch/x86/kvm/svm/svm.c
+++ b/arch/x86/kvm/svm/svm.c
@@ -4111,6 +4111,11 @@ static int svm_has_interrupt(struct kvm_vcpu *vcpu)
 	return ret;
 }
 
+static bool svm_is_bypass_apic_active(struct kvm_vcpu *vcpu)
+{
+	return sev_snp_is_ai_active(vcpu);
+}
+
 static void svm_enable_irq_window(struct kvm_vcpu *vcpu)
 {
 	struct vcpu_svm *svm = to_svm(vcpu);
@@ -5446,6 +5451,7 @@ struct kvm_x86_ops svm_x86_ops __initdata = {
 	.get_interrupt_shadow = svm_get_interrupt_shadow,
 	.patch_hypercall = svm_patch_hypercall,
 	.has_interrupt = svm_has_interrupt,
+	.is_bypass_apic_active = svm_is_bypass_apic_active,
 	.inject_irq = svm_inject_irq,
 	.inject_nmi = svm_inject_nmi,
 	.is_vnmi_pending = svm_is_vnmi_pending,
-- 
2.43.0