[Part2,RFC,v3,23/37] KVM: SVM: Add KVM_SEV_SNP_LAUNCH_FINISH command

Commit Message

Brijesh Singh June 2, 2021, 2:10 p.m. UTC

The KVM_SEV_SNP_LAUNCH_FINISH finalize the cryptographic digest and stores
it as the measurement of the guest at launch.

While finalizing the launch flow, it also issues the LAUNCH_UPDATE command
to encrypt the VMSA pages.

Signed-off-by: Brijesh Singh <[e-mail]>
---
 arch/x86/kvm/svm/sev.c   | 125 +++++++++++++++++++++++++++++++++++++++
 include/uapi/linux/kvm.h |  13 ++++
 2 files changed, 138 insertions(+)

Patch

diff --git a/arch/x86/kvm/svm/sev.c b/arch/x86/kvm/svm/sev.c
index 6b7c8287eada..856a6cf99a61 100644
--- a/arch/x86/kvm/svm/sev.c
+++ b/arch/x86/kvm/svm/sev.c
@@ -1741,6 +1741,111 @@  static int snp_launch_update(struct kvm *kvm, struct kvm_sev_cmd *argp)
 	return ret;
 }
 
+static int snp_launch_update_vmsa(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct sev_data_snp_launch_update data = {};
+	int i, ret;
+
+	data.gctx_paddr = __psp_pa(sev->snp_context);
+	data.page_type = SNP_PAGE_TYPE_VMSA;
+
+	for (i = 0; i < kvm->created_vcpus; i++) {
+		struct vcpu_svm *svm = to_svm(kvm->vcpus[i]);
+		struct rmpupdate e = {};
+
+		/* Perform some pre-encryption checks against the VMSA */
+		ret = sev_es_sync_vmsa(svm);
+		if (ret)
+			return ret;
+
+		/* Transition the VMSA page to a firmware state. */
+		e.assigned = 1;
+		e.immutable = 1;
+		e.asid = sev->asid;
+		e.gpa = -1;
+		e.pagesize = RMP_PG_SIZE_4K;
+		ret = rmpupdate(virt_to_page(svm->vmsa), &e);
+		if (ret)
+			return ret;
+
+		/* Issue the SNP command to encrypt the VMSA */
+		data.address = __sme_pa(svm->vmsa);
+		ret = __sev_issue_cmd(argp->sev_fd, SEV_CMD_SNP_LAUNCH_UPDATE,
+				      &data, &argp->error);
+		if (ret) {
+			snp_page_reclaim(virt_to_page(svm->vmsa), RMP_PG_SIZE_4K);
+			return ret;
+		}
+
+		svm->vcpu.arch.guest_state_protected = true;
+	}
+
+	return 0;
+}
+
+static int snp_launch_finish(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &to_kvm_svm(kvm)->sev_info;
+	struct sev_data_snp_launch_finish *data;
+	void *id_block = NULL, *id_auth = NULL;
+	struct kvm_sev_snp_launch_finish params;
+	int ret;
+
+	if (!sev_snp_guest(kvm))
+		return -ENOTTY;
+
+	if (!sev->snp_context)
+		return -EINVAL;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+		return -EFAULT;
+
+	/* Measure all vCPUs using LAUNCH_UPDATE before we finalize the launch flow. */
+	ret = snp_launch_update_vmsa(kvm, argp);
+	if (ret)
+		return ret;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL_ACCOUNT);
+	if (!data)
+		return -ENOMEM;
+
+	if (params.id_block_en) {
+		id_block = psp_copy_user_blob(params.id_block_uaddr, KVM_SEV_SNP_ID_BLOCK_SIZE);
+		if (IS_ERR(id_block)) {
+			ret = PTR_ERR(id_block);
+			goto e_free;
+		}
+
+		data->id_block_en = 1;
+		data->id_block_paddr = __sme_pa(id_block);
+	}
+
+	if (params.auth_key_en) {
+		id_auth = psp_copy_user_blob(params.id_auth_uaddr, KVM_SEV_SNP_ID_AUTH_SIZE);
+		if (IS_ERR(id_auth)) {
+			ret = PTR_ERR(id_auth);
+			goto e_free_id_block;
+		}
+
+		data->auth_key_en = 1;
+		data->id_auth_paddr = __sme_pa(id_auth);
+	}
+
+	data->gctx_paddr = __psp_pa(sev->snp_context);
+	ret = sev_issue_cmd(kvm, SEV_CMD_SNP_LAUNCH_FINISH, data, &argp->error);
+
+	kfree(id_auth);
+
+e_free_id_block:
+	kfree(id_block);
+
+e_free:
+	kfree(data);
+
+	return ret;
+}
+
 int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -1836,6 +1941,9 @@  int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_SNP_LAUNCH_UPDATE:
 		r = snp_launch_update(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_SNP_LAUNCH_FINISH:
+		r = snp_launch_finish(kvm, &sev_cmd);
+		break;
 	default:
 		r = -EINVAL;
 		goto out;
@@ -2324,8 +2432,25 @@  void sev_free_vcpu(struct kvm_vcpu *vcpu)
 
 	if (vcpu->arch.guest_state_protected)
 		sev_flush_guest_memory(svm, svm->vmsa, PAGE_SIZE);
+
+	/*
+	 * If its an SNP guest, then VMSA was added in the RMP entry as a guest owned page.
+	 * Transition the page to hyperivosr state before releasing it back to the system.
+	 */
+	if (sev_snp_guest(vcpu->kvm)) {
+		struct rmpupdate e = {};
+		int rc;
+
+		rc = rmpupdate(virt_to_page(svm->vmsa), &e);
+		if (rc) {
+			pr_err("Failed to release SNP guest VMSA page (rc %d), leaking it\n", rc);
+			goto skip_vmsa_free;
+		}
+	}
+
 	__free_page(virt_to_page(svm->vmsa));
 
+skip_vmsa_free:
 	if (svm->ghcb_sa_free)
 		kfree(svm->ghcb_sa);
 }
diff --git a/include/uapi/linux/kvm.h b/include/uapi/linux/kvm.h
index 8890d5a340be..8db12055b8b9 100644
--- a/include/uapi/linux/kvm.h
+++ b/include/uapi/linux/kvm.h
@@ -1682,6 +1682,7 @@  enum sev_cmd_id {
 	KVM_SEV_SNP_INIT = 255,
 	KVM_SEV_SNP_LAUNCH_START,
 	KVM_SEV_SNP_LAUNCH_UPDATE,
+	KVM_SEV_SNP_LAUNCH_FINISH,
 
 	KVM_SEV_NR_MAX,
 };
@@ -1693,6 +1694,18 @@  struct kvm_sev_cmd {
 	__u32 sev_fd;
 };
 
+#define KVM_SEV_SNP_ID_BLOCK_SIZE	96
+#define KVM_SEV_SNP_ID_AUTH_SIZE	4096
+#define KVM_SEV_SNP_FINISH_DATA_SIZE	32
+
+struct kvm_sev_snp_launch_finish {
+	__u64 id_block_uaddr;
+	__u64 id_auth_uaddr;
+	__u8 id_block_en;
+	__u8 auth_key_en;
+	__u8 host_data[KVM_SEV_SNP_FINISH_DATA_SIZE];
+};
+
 struct kvm_sev_launch_start {
 	__u32 handle;
 	__u32 policy;