[RFC PATCH v1 1/3] x86/tdx: Make TDX metadata available via SYSFS

[Alexey Gladkov <legion@kernel.org>]

From: "Alexey Gladkov (Intel)" <legion@kernel.org>

Expose the TDX module information to userspace. The version information
is valuable for debugging, as knowing the exact module version can help
reproduce TDX-related issues.

Signed-off-by: Alexey Gladkov (Intel) <legion@kernel.org>
---
 arch/x86/Kconfig                  |  1 +
 arch/x86/include/asm/shared/tdx.h |  2 +
 arch/x86/include/asm/tdx.h        | 12 +++++
 arch/x86/virt/vmx/tdx/tdx.c       | 74 +++++++++++++++++++++++++++++++
 4 files changed, 89 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index be2c311f5118..516f3539d0c7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -1986,6 +1986,7 @@ config INTEL_TDX_HOST
 	depends on CONTIG_ALLOC
 	depends on !KEXEC_CORE
 	depends on X86_MCE
+	select SYS_HYPERVISOR
 	help
 	  Intel Trust Domain Extensions (TDX) protects guest VMs from malicious
 	  host and certain physical attacks.  This option enables necessary TDX
diff --git a/arch/x86/include/asm/shared/tdx.h b/arch/x86/include/asm/shared/tdx.h
index 606d93a1cbac..92ee9dfb21e7 100644
--- a/arch/x86/include/asm/shared/tdx.h
+++ b/arch/x86/include/asm/shared/tdx.h
@@ -18,6 +18,8 @@
 #define TDG_MEM_PAGE_ACCEPT		6
 #define TDG_VM_RD			7
 #define TDG_VM_WR			8
+/* TDG_SYS_RD is available since TDX module version 1.5 and later. */
+#define TDG_SYS_RD			11
 
 /* TDX attributes */
 #define TDX_ATTR_DEBUG_BIT		0
diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index e6b003fe7f5e..95d748bc8464 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -31,6 +31,18 @@
 #define TDX_SUCCESS		0ULL
 #define TDX_RND_NO_ENTROPY	0x8000020300000000ULL
 
+/*
+ * TDX metadata base field id, used by TDCALL TDG.SYS.RD
+ * See TDX ABI Spec Global Metadata Fields
+ */
+#define TDX_SYS_MINOR_FID		0x0800000100000003ULL
+#define TDX_SYS_MAJOR_FID		0x0800000100000004ULL
+#define TDX_SYS_UPDATE_FID		0x0800000100000005ULL
+#define TDX_SYS_INTERNAL_FID		0x0800000100000006ULL
+#define TDX_SYS_BUILD_DATE_FID		0x8800000200000001ULL
+#define TDX_SYS_BUILD_NUM_FID		0x8800000100000002ULL
+#define TDX_SYS_FEATURES0_FID		0x0A00000300000008ULL
+
 #ifndef __ASSEMBLY__
 
 #include <uapi/asm/mce.h>
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index f5e2a937c1e7..89378e2a1f66 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -1869,3 +1869,77 @@ u64 tdh_phymem_page_wbinvd_hkid(u64 hkid, struct page *page)
 	return seamcall(TDH_PHYMEM_PAGE_WBINVD, &args);
 }
 EXPORT_SYMBOL_GPL(tdh_phymem_page_wbinvd_hkid);
+
+#ifdef CONFIG_SYSFS
+#define TDX_SYSFS_ATTR(_field, _name, fmt)				\
+static ssize_t _name ## _show(						\
+	struct kobject *kobj, struct kobj_attribute *attr, char *buf)	\
+{									\
+	u64 value = 0;							\
+	read_sys_metadata_field(_field, &value);			\
+	return sprintf(buf, fmt, value);				\
+}									\
+static struct kobj_attribute _name ## _attr = __ATTR_RO(_name)
+
+TDX_SYSFS_ATTR(TDX_SYS_MINOR_FID, minor, "%lld\n");
+TDX_SYSFS_ATTR(TDX_SYS_MAJOR_FID, major, "%lld\n");
+TDX_SYSFS_ATTR(TDX_SYS_UPDATE_FID, update, "%lld\n");
+TDX_SYSFS_ATTR(TDX_SYS_BUILD_NUM_FID, build_num, "%lld\n");
+TDX_SYSFS_ATTR(TDX_SYS_BUILD_DATE_FID, build_date, "%lld\n");
+TDX_SYSFS_ATTR(TDX_SYS_FEATURES0_FID, features0, "%llx\n");
+
+static struct attribute *version_attrs[] = {
+	&minor_attr.attr,
+	&major_attr.attr,
+	&update_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group version_attr_group = {
+	.name = "version",
+	.attrs = version_attrs,
+};
+
+static struct attribute *properties_attrs[] = {
+	&build_num_attr.attr,
+	&build_date_attr.attr,
+	&features0_attr.attr,
+	NULL,
+};
+
+static const struct attribute_group properties_attr_group = {
+	.name = "properties",
+	.attrs = properties_attrs,
+};
+
+__init static int tdh_sysfs_init(void)
+{
+	struct kobject *tdx_kobj;
+	int ret;
+
+	if (!hypervisor_kobj)
+		return -ENOMEM;
+
+	tdx_kobj = kobject_create_and_add("tdx", hypervisor_kobj);
+
+	if (!tdx_kobj)
+		return -ENOMEM;
+
+	ret = sysfs_create_group(tdx_kobj, &version_attr_group);
+	if (ret)
+		pr_err("sysfs exporting tdx module version failed %d\n", ret);
+
+	if (!ret) {
+		ret = sysfs_create_group(tdx_kobj, &properties_attr_group);
+		if (ret)
+			pr_err("sysfs exporting tdx module features failed %d\n", ret);
+	}
+
+	if (ret)
+		kobject_put(tdx_kobj);
+
+	return ret;
+}
+
+arch_initcall(tdh_sysfs_init);
+#endif // CONFIG_SYSFS
-- 
2.48.1