3 files changed, 246 insertions, 0 deletions
diff --git a/drivers/virt/coco/tdx-host/Kconfig b/drivers/virt/coco/tdx-host/Kconfig
new file mode 100644
index 000000000..57d0c01a4
--- /dev/null
+++ b/drivers/virt/coco/tdx-host/Kconfig
@@ -0,0 +1,6 @@
+config TDX_HOST_SERVICES
+	tristate
+	depends on INTEL_TDX_HOST
+	select FW_LOADER
+	select FW_UPLOAD
+	default m
diff --git a/drivers/virt/coco/tdx-host/Makefile b/drivers/virt/coco/tdx-host/Makefile
new file mode 100644
index 000000000..e61e749a8
--- /dev/null
+++ b/drivers/virt/coco/tdx-host/Makefile
@@ -0,0 +1 @@
+obj-$(CONFIG_TDX_HOST_SERVICES) += tdx-host.o
diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
new file mode 100644
index 000000000..d48952968
--- /dev/null
+++ b/drivers/virt/coco/tdx-host/tdx-host.c
@@ -0,0 +1,239 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * TDX host user interface driver
+ *
+ * Copyright (C) 2025 Intel Corporation
+ */
+
+#include <linux/device/faux.h>
+#include <linux/firmware.h>
+#include <linux/module.h>
+#include <linux/mod_devicetable.h>
+#include <linux/sysfs.h>
+
+#include <asm/cpu_device_id.h>
+#include <asm/seamldr.h>
+#include <asm/tdx.h>
+
+static const struct x86_cpu_id tdx_host_ids[] = {
+	X86_MATCH_FEATURE(X86_FEATURE_TDX_HOST_PLATFORM, NULL),
+	{}
+};
+MODULE_DEVICE_TABLE(x86cpu, tdx_host_ids);
+
+static ssize_t version_show(struct device *dev, struct device_attribute *attr,
+			    char *buf)
+{
+	const struct tdx_sys_info *tdx_sysinfo = tdx_get_sysinfo();
+	const struct tdx_sys_info_version *ver;
+	int ret;
+
+	if (!tdx_sysinfo)
+		return -ENXIO;
+
+	/*
+	 * The version number can change during an update.
+	 * Lock out updates while printing the version.
+	 */
+	seamldr_lock_module_update();
+
+	ver = &tdx_sysinfo->version;
+	ret = sysfs_emit(buf, TDX_VERSION_FMT "\n", ver->major_version,
+						    ver->minor_version,
+						    ver->update_version);
+	seamldr_unlock_module_update();
+
+	return ret;
+}
+static DEVICE_ATTR_RO(version);
+
+static struct attribute *tdx_host_attrs[] = {
+	&dev_attr_version.attr,
+	NULL,
+};
+
+static const struct attribute_group tdx_host_group = {
+	.attrs = tdx_host_attrs,
+};
+
+static ssize_t seamldr_version_show(struct device *dev, struct device_attribute *attr,
+				    char *buf)
+{
+	struct seamldr_info info;
+	int ret;
+
+	ret = seamldr_get_info(&info);
+	if (ret)
+		return ret;
+
+	return sysfs_emit(buf, TDX_VERSION_FMT "\n", info.major_version,
+						     info.minor_version,
+						     info.update_version);
+}
+
+static ssize_t num_remaining_updates_show(struct device *dev,
+					  struct device_attribute *attr,
+					  char *buf)
+{
+	struct seamldr_info info;
+	int ret;
+
+	ret = seamldr_get_info(&info);
+	if (ret)
+		return ret;
+
+	return sysfs_emit(buf, "%u\n", info.num_remaining_updates);
+}
+
+/*
+ * These attributes are intended for managing TDX module updates. Reading
+ * them issues a slow, serialized P-SEAMLDR query, so keep them admin-only.
+ */
+static DEVICE_ATTR_ADMIN_RO(seamldr_version);
+static DEVICE_ATTR_ADMIN_RO(num_remaining_updates);
+
+static struct attribute *seamldr_attrs[] = {
+	&dev_attr_seamldr_version.attr,
+	&dev_attr_num_remaining_updates.attr,
+	NULL,
+};
+
+static bool supports_runtime_update(void)
+{
+	const struct tdx_sys_info *sysinfo = tdx_get_sysinfo();
+
+	if (!sysinfo)
+		return false;
+
+	if (!tdx_supports_runtime_update(sysinfo))
+		return false;
+
+	/*
+	 * This bug makes P-SEAMLDR calls clobber the current VMCS
+	 * which breaks KVM. Avoid P-SEAMLDR calls by hiding all
+	 * attributes if the CPU has this bug.
+	 */
+	if (boot_cpu_has_bug(X86_BUG_SEAMRET_INVD_VMCS))
+		return false;
+
+	return true;
+}
+
+static umode_t seamldr_group_visible(struct kobject *kobj, struct attribute *attr, int idx)
+{
+	if (!supports_runtime_update())
+		return 0;
+
+	return attr->mode;
+}
+
+static const struct attribute_group seamldr_group = {
+	.attrs = seamldr_attrs,
+	.is_visible = seamldr_group_visible,
+};
+
+static const struct attribute_group *tdx_host_groups[] = {
+	&tdx_host_group,
+	&seamldr_group,
+	NULL,
+};
+
+static enum fw_upload_err tdx_fw_prepare(struct fw_upload *fwl,
+					 const u8 *data, u32 data_len)
+{
+	return FW_UPLOAD_ERR_NONE;
+}
+
+static enum fw_upload_err tdx_fw_write(struct fw_upload *fwl, const u8 *data,
+				       u32 offset, u32 data_len, u32 *written)
+{
+	int ret;
+
+	ret = seamldr_install_module(data, data_len);
+	switch (ret) {
+	case 0:
+		*written = data_len;
+		return FW_UPLOAD_ERR_NONE;
+	default:
+		return FW_UPLOAD_ERR_FW_INVALID;
+	}
+}
+
+static enum fw_upload_err tdx_fw_poll_complete(struct fw_upload *fwl)
+{
+	/*
+	 * The upload completed during tdx_fw_write().
+	 * Never poll for completion.
+	 */
+	return FW_UPLOAD_ERR_NONE;
+}
+
+static void tdx_fw_cancel(struct fw_upload *fwl)
+{
+	/*
+	 * TDX module updates are not cancellable.
+	 * Provide a no-op callback to satisfy fw_upload_ops.
+	 */
+}
+
+static const struct fw_upload_ops tdx_fw_ops = {
+	.prepare	= tdx_fw_prepare,
+	.write		= tdx_fw_write,
+	.poll_complete	= tdx_fw_poll_complete,
+	.cancel		= tdx_fw_cancel,
+};
+
+static void seamldr_deinit(void *tdx_fwl)
+{
+	firmware_upload_unregister(tdx_fwl);
+}
+
+static int seamldr_init(struct device *dev)
+{
+	struct fw_upload *tdx_fwl;
+
+	if (!supports_runtime_update())
+		return 0;
+
+	tdx_fwl = firmware_upload_register(THIS_MODULE, dev, "tdx_module",
+					   &tdx_fw_ops, NULL);
+	if (IS_ERR(tdx_fwl))
+		return PTR_ERR(tdx_fwl);
+
+	return devm_add_action_or_reset(dev, seamldr_deinit, tdx_fwl);
+}
+
+static int tdx_host_probe(struct faux_device *fdev)
+{
+	return seamldr_init(&fdev->dev);
+}
+
+static const struct faux_device_ops tdx_host_ops = {
+	.probe		= tdx_host_probe,
+};
+
+static struct faux_device *fdev;
+
+static int __init tdx_host_init(void)
+{
+	if (!x86_match_cpu(tdx_host_ids) || !tdx_get_sysinfo())
+		return -ENODEV;
+
+	fdev = faux_device_create_with_groups(KBUILD_MODNAME, NULL,
+					      &tdx_host_ops,
+					      tdx_host_groups);
+	if (!fdev)
+		return -ENODEV;
+
+	return 0;
+}
+module_init(tdx_host_init);
+
+static void __exit tdx_host_exit(void)
+{
+	faux_device_destroy(fdev);
+}
+module_exit(tdx_host_exit);
+
+MODULE_DESCRIPTION("TDX Host Services");
+MODULE_LICENSE("GPL");