KVM: SVM: Add support for KVM_SEV_LAUNCH_START command

The KVM_SEV_LAUNCH_START command is used to create a memory encryption
context within the SEV firmware. In order to do so, the guest owner
should provide the guest's policy, its public Diffie-Hellman (PDH) key
and session information. The command implements the LAUNCH_START flow
defined in SEV spec Section 6.2.

Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: "Radim Krčmář" <rkrcmar@redhat.com>
Cc: Joerg Roedel <joro@8bytes.org>
Cc: Borislav Petkov <bp@suse.de>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: x86@kernel.org
Cc: kvm@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Improvements-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Brijesh Singh <brijesh.singh@amd.com>
Reviewed-by: Borislav Petkov <bp@suse.de>

arch/x86/include/asm/kvm_host.h

@@ -750,6 +750,8 @@ enum kvm_irqchip_mode {
 struct kvm_sev_info {
 	bool active;		/* SEV enabled guest */
 	unsigned int asid;	/* ASID used for this guest */
+	unsigned int handle;	/* SEV firmware handle */
+	int fd;			/* SEV device fd */
 };
 
 struct kvm_arch {

arch/x86/kvm/svm.c

@@ -1538,11 +1538,45 @@ static void sev_asid_free(struct kvm *kvm)
 	__sev_asid_free(sev->asid);
 }
 
+static void sev_unbind_asid(struct kvm *kvm, unsigned int handle)
+{
+	struct sev_data_decommission *decommission;
+	struct sev_data_deactivate *data;
+
+	if (!handle)
+		return;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return;
+
+	/* deactivate handle */
+	data->handle = handle;
+	sev_guest_deactivate(data, NULL);
+
+	wbinvd_on_all_cpus();
+	sev_guest_df_flush(NULL);
+	kfree(data);
+
+	decommission = kzalloc(sizeof(*decommission), GFP_KERNEL);
+	if (!decommission)
+		return;
+
+	/* decommission handle */
+	decommission->handle = handle;
+	sev_guest_decommission(decommission, NULL);
+
+	kfree(decommission);
+}
+
 static void sev_vm_destroy(struct kvm *kvm)
 {
+	struct kvm_sev_info *sev = &kvm->arch.sev_info;
+
 	if (!sev_guest(kvm))
 		return;
 
+	sev_unbind_asid(kvm, sev->handle);
 	sev_asid_free(kvm);
 }
 
@@ -5708,6 +5742,122 @@ e_free:
 	return ret;
 }
 
+static int sev_bind_asid(struct kvm *kvm, unsigned int handle, int *error)
+{
+	struct sev_data_activate *data;
+	int asid = sev_get_asid(kvm);
+	int ret;
+
+	wbinvd_on_all_cpus();
+
+	ret = sev_guest_df_flush(error);
+	if (ret)
+		return ret;
+
+	data = kzalloc(sizeof(*data), GFP_KERNEL);
+	if (!data)
+		return -ENOMEM;
+
+	/* activate ASID on the given handle */
+	data->handle = handle;
+	data->asid   = asid;
+	ret = sev_guest_activate(data, error);
+	kfree(data);
+
+	return ret;
+}
+
+static int sev_issue_cmd(int fd, int id, void *data, int *error)
+{
+	struct fd f;
+	int ret;
+
+	f = fdget(fd);
+	if (!f.file)
+		return -EBADF;
+
+	ret = sev_issue_cmd_external_user(f.file, id, data, error);
+
+	fdput(f);
+	return ret;
+}
+
+static int sev_launch_start(struct kvm *kvm, struct kvm_sev_cmd *argp)
+{
+	struct kvm_sev_info *sev = &kvm->arch.sev_info;
+	struct sev_data_launch_start *start;
+	struct kvm_sev_launch_start params;
+	void *dh_blob, *session_blob;
+	int *error = &argp->error;
+	int ret;
+
+	if (!sev_guest(kvm))
+		return -ENOTTY;
+
+	if (copy_from_user(&params, (void __user *)(uintptr_t)argp->data, sizeof(params)))
+		return -EFAULT;
+
+	start = kzalloc(sizeof(*start), GFP_KERNEL);
+	if (!start)
+		return -ENOMEM;
+
+	dh_blob = NULL;
+	if (params.dh_uaddr) {
+		dh_blob = psp_copy_user_blob(params.dh_uaddr, params.dh_len);
+		if (IS_ERR(dh_blob)) {
+			ret = PTR_ERR(dh_blob);
+			goto e_free;
+		}
+
+		start->dh_cert_address = __sme_set(__pa(dh_blob));
+		start->dh_cert_len = params.dh_len;
+	}
+
+	session_blob = NULL;
+	if (params.session_uaddr) {
+		session_blob = psp_copy_user_blob(params.session_uaddr, params.session_len);
+		if (IS_ERR(session_blob)) {
+			ret = PTR_ERR(session_blob);
+			goto e_free_dh;
+		}
+
+		start->session_address = __sme_set(__pa(session_blob));
+		start->session_len = params.session_len;
+	}
+
+	start->handle = params.handle;
+	start->policy = params.policy;
+
+	/* create memory encryption context */
+	ret = sev_issue_cmd(argp->sev_fd, SEV_CMD_LAUNCH_START, start, error);
+	if (ret)
+		goto e_free_session;
+
+	/* Bind ASID to this guest */
+	ret = sev_bind_asid(kvm, start->handle, error);
+	if (ret)
+		goto e_free_session;
+
+	/* return handle to userspace */
+	params.handle = start->handle;
+	if (copy_to_user((void __user *)(uintptr_t)argp->data, &params, sizeof(params))) {
+		sev_unbind_asid(kvm, start->handle);
+		ret = -EFAULT;
+		goto e_free_session;
+	}
+
+	sev->handle = start->handle;
+	sev->fd = argp->sev_fd;
+
+e_free_session:
+	kfree(session_blob);
+e_free_dh:
+	kfree(dh_blob);
+e_free:
+	kfree(start);
+	return ret;
+}
+
 static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 {
 	struct kvm_sev_cmd sev_cmd;
@@ -5725,6 +5875,9 @@ static int svm_mem_enc_op(struct kvm *kvm, void __user *argp)
 	case KVM_SEV_INIT:
 		r = sev_guest_init(kvm, &sev_cmd);
 		break;
+	case KVM_SEV_LAUNCH_START:
+		r = sev_launch_start(kvm, &sev_cmd);
+		break;
 	default:
 		r = -EINVAL;
 		goto out;