[PATCH v2 2/3] coco/tdx-host: Expose TDX Module version

[Chao Gao <chao.gao@intel.com>]

Currently there is no way to know the TDX Module version from the
userspace. Such information is always helpful for bug reporting or
debugging.

With the tdx-host device in place, expose the TDX Module version as
a device attribute via sysfs.

Signed-off-by: Chao Gao <chao.gao@intel.com>
---
v2: 
 - No need to update MAINTAINERS to include sysfs-devices-faux-tdx-host
   explicitly (Kirill)

 .../ABI/testing/sysfs-devices-faux-tdx-host   |  6 +++++
 drivers/virt/coco/tdx-host/tdx-host.c         | 26 ++++++++++++++++++-
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100644 Documentation/ABI/testing/sysfs-devices-faux-tdx-host

diff --git a/Documentation/ABI/testing/sysfs-devices-faux-tdx-host b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
new file mode 100644
index 000000000000..35ef21f53c2e
--- /dev/null
+++ b/Documentation/ABI/testing/sysfs-devices-faux-tdx-host
@@ -0,0 +1,6 @@
+What:		/sys/devices/faux/tdx_host/version
+Contact:	linux-coco@lists.linux.dev
+Description:	(RO) Report the version of the loaded TDX Module. The TDX Module
+		version is formatted as x.y.z, where "x" is the major version,
+		"y" is the minor version and "z" is the update version. Versions
+		are used for bug reporting, TD-Preserving updates and etc.
diff --git a/drivers/virt/coco/tdx-host/tdx-host.c b/drivers/virt/coco/tdx-host/tdx-host.c
index ced1c980dc6f..2883c6638faf 100644
--- a/drivers/virt/coco/tdx-host/tdx-host.c
+++ b/drivers/virt/coco/tdx-host/tdx-host.c
@@ -9,6 +9,7 @@
 #include <linux/mod_devicetable.h>
 #include <linux/device/faux.h>
 #include <asm/cpu_device_id.h>
+#include <asm/tdx.h>
 
 static const struct x86_cpu_id tdx_host_ids[] = {
 	X86_MATCH_FEATURE(X86_FEATURE_TDX_HOST_PLATFORM, NULL),
@@ -18,12 +19,35 @@ MODULE_DEVICE_TABLE(x86cpu, tdx_host_ids);
 
 static struct faux_device *fdev;
 
+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;
+
+	if (!tdx_sysinfo)
+		return -ENXIO;
+
+	ver = &tdx_sysinfo->version;
+
+	return sysfs_emit(buf, "%u.%u.%02u\n", ver->major_version,
+					       ver->minor_version,
+					       ver->update_version);
+}
+static DEVICE_ATTR_RO(version);
+
+static struct attribute *tdx_host_attrs[] = {
+	&dev_attr_version.attr,
+	NULL,
+};
+ATTRIBUTE_GROUPS(tdx_host);
+
 static int __init tdx_host_init(void)
 {
 	if (!x86_match_cpu(tdx_host_ids))
 		return -ENODEV;
 
-	fdev = faux_device_create(KBUILD_MODNAME, NULL, NULL);
+	fdev = faux_device_create_with_groups(KBUILD_MODNAME, NULL, NULL, tdx_host_groups);
 	if (!fdev)
 		return -ENODEV;
 
-- 
2.47.3