[PATCH RFC v9 37/51] KVM: SVM: Add support to handle Page State Change VMGEXIT

[Michael Roth]

From: Brijesh Singh <brijesh.singh@xxxxxxx>

SEV-SNP VMs can ask the hypervisor to change the page state in the RMP
table to be private or shared using the Page State Change NAE event
as defined in the GHCB specification version 2.

Forward these requests to userspace as KVM_EXIT_VMGEXITs, similar to how
it is done for requests that don't use a GHCB page.

Co-developed-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Michael Roth <michael.roth@xxxxxxx>
Signed-off-by: Brijesh Singh <brijesh.singh@xxxxxxx>
Signed-off-by: Ashish Kalra <ashish.kalra@xxxxxxx>
---
 arch/x86/kvm/svm/sev.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 2afc59b86b91..9b9dff7728c8 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -3039,6 +3039,7 @@ static int sev_es_validate_vmgexit(struct vcpu_svm *svm)
 	case SVM_VMGEXIT_AP_JUMP_TABLE:
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
 	case SVM_VMGEXIT_HV_FEATURES:
+	case SVM_VMGEXIT_PSC:
 		break;
 	default:
 		reason = GHCB_ERR_INVALID_EVENT;
@@ -3242,6 +3243,15 @@ static int snp_complete_psc_msr_protocol(struct kvm_vcpu *vcpu)
 	return 1; /* resume */
 }
 
+static int snp_complete_psc(struct kvm_vcpu *vcpu)
+{
+	struct vcpu_svm *svm = to_svm(vcpu);
+
+	ghcb_set_sw_exit_info_2(svm->sev_es.ghcb, vcpu->run->vmgexit.ret);
+
+	return 1; /* resume */
+}
+
 static int sev_handle_vmgexit_msr_protocol(struct vcpu_svm *svm)
 {
 	struct vmcb_control_area *control = &svm->vmcb->control;
@@ -3485,6 +3495,12 @@ int sev_handle_vmgexit(struct kvm_vcpu *vcpu)
 		ret = 1;
 		break;
 	}
+	case SVM_VMGEXIT_PSC:
+		/* Let userspace handling allocating/deallocating backing pages. */
+		vcpu->run->exit_reason = KVM_EXIT_VMGEXIT;
+		vcpu->run->vmgexit.ghcb_msr = ghcb_gpa;
+		vcpu->arch.complete_userspace_io = snp_complete_psc;
+		break;
 	case SVM_VMGEXIT_UNSUPPORTED_EVENT:
 		vcpu_unimpl(vcpu,
 			    "vmgexit: unsupported event - exit_info_1=%#llx, exit_info_2=%#llx\n",
-- 
2.25.1