[PATCH v6 6/7] KVM: SVM: Add support for Hypervisor Feature support MSR protocol

[Joerg Roedel <joro@xxxxxxxxxx>]

From: Brijesh Singh <brijesh.singh@xxxxxxx>

Version 2 of the GHCB specification introduced advertisement of
supported Hypervisor SEV features. This request is required to support
a the GHCB version 2 protocol.

Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
---
 arch/x86/include/uapi/asm/svm.h |  1 +
 arch/x86/kvm/svm/sev.c          | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+)

diff --git a/arch/x86/include/uapi/asm/svm.h b/arch/x86/include/uapi/asm/svm.h
index efa969325ede..67cf153fe580 100644
--- a/arch/x86/include/uapi/asm/svm.h
+++ b/arch/x86/include/uapi/asm/svm.h
@@ -108,6 +108,7 @@
 #define SVM_VMGEXIT_AP_JUMP_TABLE		0x80000005
 #define SVM_VMGEXIT_SET_AP_JUMP_TABLE		0
 #define SVM_VMGEXIT_GET_AP_JUMP_TABLE		1
+#define SVM_VMGEXIT_HYPERVISOR_FEATURES		0x8000fffd
 #define SVM_VMGEXIT_UNSUPPORTED_EVENT		0x8000ffff
 
 /* Exit code reserved for hypervisor/software use */
diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 1219c1771895..403f24498020 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -2452,6 +2452,7 @@ static bool sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	case SVM_VMGEXIT_AP_HLT_LOOP:
 	case SVM_VMGEXIT_AP_JUMP_TABLE:
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
+	case SVM_VMGEXIT_HYPERVISOR_FEATURES:
 		break;
 	default:
 		reason = GHCB_ERR_INVALID_EVENT;
@@ -2689,6 +2690,19 @@ static int sev_emulate_ap_reset_hold(struct vcpu_svm *svm, u64 hold_type)
 				  KVM_MP_STATE_AP_RESET_HOLD, KVM_EXIT_AP_RESET_HOLD) && ret;
 }
 
+/* Hypervisor GHCB Features supported by KVM */
+#define KVM_SUPPORTED_GHCB_HV_FEATURES		0UL
+
+static u64 ghcb_msr_hv_feat_resp(void)
+{
+	u64 msr;
+
+	msr  = GHCB_MSR_HV_FT_RESP;
+	msr |= (KVM_SUPPORTED_GHCB_HV_FEATURES << GHCB_DATA_LOW);
+
+	return msr;
+}
+
 static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -2738,6 +2752,9 @@ static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 	case GHCB_MSR_AP_RESET_HOLD_REQ:
 		ret = sev_emulate_ap_reset_hold(svm, GHCB_MSR_AP_RESET_HOLD_REQ);
 		break;
+	case GHCB_MSR_HV_FT_REQ:
+		svm->vmcb->control.ghcb_gpa = ghcb_msr_hv_feat_resp();
+		break;
 	case GHCB_MSR_TERM_REQ: {
 		u64 reason_set, reason_code;
 
@@ -2851,6 +2868,11 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 
 		break;
 	}
+	case SVM_VMGEXIT_HYPERVISOR_FEATURES:
+		ghcb_set_sw_exit_info_2(ghcb, KVM_SUPPORTED_GHCB_HV_FEATURES);
+
+		ret = 1;
+		break;
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
 		vcpu_unimpl(vcpu,
 			    "vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
-- 
2.34.1