To support the SEV-SNP Restricted Injection feature, the SEV-SNP guest must
register a #HV doorbell page for use with the #HV.

The #HV doorbell page NAE event allows the guest to register a #HV doorbell
page. The NAE event consists of four actions: GET_PREFERRED, SET, QUERY, CLEAR.
Implement the NAE event as per GHCB specification.

Co-developed-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Thomas Lendacky <thomas.lendacky@amd.com>
Signed-off-by: Melody Wang <huibo.wang@amd.com>
---
 arch/x86/include/uapi/asm/svm.h |  5 +++
 arch/x86/kvm/svm/sev.c          | 73 +++++++++++++++++++++++++++++++++
 arch/x86/kvm/svm/svm.h          |  2 +
 3 files changed, 80 insertions(+)

diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index 1814b413fd57..7905c9be44d1 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -115,6 +115,11 @@
 #define SVM_VMGEXIT_AP_CREATE_ON_INIT		0
 #define SVM_VMGEXIT_AP_CREATE			1
 #define SVM_VMGEXIT_AP_DESTROY			2
+#define SVM_VMGEXIT_HVDB_PAGE                   0x80000014
+#define SVM_VMGEXIT_HVDB_GET_PREFERRED          0
+#define SVM_VMGEXIT_HVDB_SET                    1
+#define SVM_VMGEXIT_HVDB_QUERY                  2
+#define SVM_VMGEXIT_HVDB_CLEAR                  3
 #define SVM_VMGEXIT_SNP_RUN_VMPL		0x80000018
 #define SVM_VMGEXIT_HV_FEATURES			0x8000fffd
 #define SVM_VMGEXIT_TERM_REQUEST		0x8000fffe
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 72674b8825c4..7cd1c0652d15 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3413,6 +3413,10 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 		    control->exit_info_1 == control->exit_info_2)
 			goto vmgexit_err;
 		break;
+	case SVM_VMGEXIT_HVDB_PAGE:
+		if (!sev_snp_guest(vcpu->kvm))
+			goto vmgexit_err;
+		break;
 	default:
 		reason = GHCB_ERR_INVALID_EVENT;
 		goto vmgexit_err;
@@ -4129,6 +4133,66 @@ static int snp_handle_ext_guest_req(struct vcpu_svm *svm, gpa_t req_gpa, gpa_t r
 	return 1; /* resume guest */
 }
 
+static int sev_snp_hv_doorbell_page(struct vcpu_svm *svm)
+{
+	struct kvm_vcpu *vcpu = &svm->vcpu;
+	struct kvm_host_map hvdb_map;
+	gpa_t hvdb_gpa;
+	u64 request;
+
+	if (!sev_snp_guest(vcpu->kvm))
+		return -EINVAL;
+
+	request = svm->vmcb->control.exit_info_1;
+	hvdb_gpa = svm->vmcb->control.exit_info_2;
+
+	switch (request) {
+	case SVM_VMGEXIT_HVDB_GET_PREFERRED:
+		ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, ~0ULL);
+		break;
+	case SVM_VMGEXIT_HVDB_SET:
+		svm->sev_es.hvdb_gpa = INVALID_PAGE;
+
+		if (!PAGE_ALIGNED(hvdb_gpa)) {
+			vcpu_unimpl(vcpu, "vmgexit: unaligned #HV doorbell page address [%#llx] from guest\n",
+				    hvdb_gpa);
+			return -EINVAL;
+		}
+
+		if (!page_address_valid(vcpu, hvdb_gpa)) {
+			vcpu_unimpl(vcpu, "vmgexit: invalid #HV doorbell page address [%#llx] from guest\n",
+				    hvdb_gpa);
+			return -EINVAL;
+		}
+
+		/* Map and unmap the GPA just to be sure the GPA is valid */
+		if (kvm_vcpu_map(vcpu, gpa_to_gfn(hvdb_gpa), &hvdb_map)) {
+			/* Unable to map #HV doorbell page from guest */
+			vcpu_unimpl(vcpu, "vmgexit: error mapping #HV doorbell page [%#llx] from guest\n",
+				    hvdb_gpa);
+			return -EINVAL;
+		}
+		kvm_vcpu_unmap(vcpu, &hvdb_map);
+
+		svm->sev_es.hvdb_gpa = hvdb_gpa;
+		fallthrough;
+	case SVM_VMGEXIT_HVDB_QUERY:
+		ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, svm->sev_es.hvdb_gpa);
+		break;
+	case SVM_VMGEXIT_HVDB_CLEAR:
+		svm->sev_es.hvdb_gpa = INVALID_PAGE;
+		break;
+	default:
+		svm->sev_es.hvdb_gpa = INVALID_PAGE;
+
+		vcpu_unimpl(vcpu, "vmgexit: invalid #HV doorbell page request [%#llx] from guest\n",
+			    request);
+		return -EINVAL;
+	}
+
+	return 0;
+}
+
 static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -4409,6 +4473,14 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 	case SVM_VMGEXIT_EXT_GUEST_REQUEST:
 		ret = snp_handle_ext_guest_req(svm, control->exit_info_1, control->exit_info_2);
 		break;
+	case SVM_VMGEXIT_HVDB_PAGE:
+		if (sev_snp_hv_doorbell_page(svm)) {
+			ghcb_set_sw_exit_info_1(svm->sev_es.ghcb, 2);
+			ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, GHCB_ERR_INVALID_INPUT);
+		}
+
+		ret = 1;
+		break;
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
 		vcpu_unimpl(vcpu,
 			    "vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
@@ -4576,6 +4648,7 @@ void sev_es_vcpu_reset(struct vcpu_svm *svm)
 					    sev_enc_bit));
 
 	mutex_init(&svm->sev_es.snp_vmsa_mutex);
+	svm->sev_es.hvdb_gpa = INVALID_PAGE;
 }
 
 void sev_es_prepare_switch_to_guest(struct vcpu_svm *svm, struct sev_es_save_area *hostsa)
diff --git a/arch/x86/kvm/svm/svm.h b/arch/x86/kvm/svm/svm.h
index 43fa6a16eb19..161bd32b87ad 100644
--- a/arch/x86/kvm/svm/svm.h
+++ b/arch/x86/kvm/svm/svm.h
@@ -239,6 +239,8 @@ struct vcpu_sev_es_state {
 	gpa_t snp_vmsa_gpa;
 	bool snp_ap_waiting_for_reset;
 	bool snp_has_guest_vmsa;
+
+	gpa_t hvdb_gpa;
 };
 
 struct vcpu_svm {
-- 
2.34.1