linux-kernel - [PATCH 6/6] x86/virt/tdx: Skip unsupported metadata by querying tdx

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Message-Id: <20251202050844.2520762-7-yilun.xu@linux.intel.com>
Date: Tue,  2 Dec 2025 13:08:44 +0800
From: Xu Yilun <yilun.xu@...ux.intel.com>
To: x86@...nel.org,
	dave.hansen@...ux.intel.com,
	kas@...nel.org,
	linux-kernel@...r.kernel.org
Cc: chao.gao@...el.com,
	rick.p.edgecombe@...el.com,
	dan.j.williams@...el.com,
	baolu.lu@...ux.intel.com,
	yilun.xu@...ux.intel.com,
	yilun.xu@...el.com,
	zhenzhong.duan@...el.com,
	kvm@...r.kernel.org,
	adrian.hunter@...el.com
Subject: [PATCH 6/6] x86/virt/tdx: Skip unsupported metadata by querying tdx_feature0

TDX Module will add new metadata fields for new features over time.
These new metadata fields are optional and only valid when the
corresponding bits in tdx_feature0 are set. Add new helpers to specify
the required feature bits for each field_id, to avoid reading
unsupported metadata fields and in turn failing the entire metadata
reading process.

Add definitions for the new metadata fields "TDX Module Extensions" as
the example.

Cc: Rick Edgecombe <rick.p.edgecombe@...el.com>
Signed-off-by: Xu Yilun <yilun.xu@...ux.intel.com>
---
 arch/x86/include/asm/tdx.h                  |  1 +
 arch/x86/include/asm/tdx_global_metadata.h  |  6 +++++
 arch/x86/virt/vmx/tdx/tdx_global_metadata.c | 25 ++++++++++++++++-----
 3 files changed, 27 insertions(+), 5 deletions(-)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index 96565f6b69b9..886d65ed58c8 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -151,6 +151,7 @@ const char *tdx_dump_mce_info(struct mce *m);
 
 /* Bit definitions of TDX_FEATURES0 metadata field */
 #define TDX_FEATURES0_NO_RBP_MOD	BIT_ULL(18)
+#define TDX_FEATURES0_EXT		BIT_ULL(39)
 
 const struct tdx_sys_info *tdx_get_sysinfo(void);
 
diff --git a/arch/x86/include/asm/tdx_global_metadata.h b/arch/x86/include/asm/tdx_global_metadata.h
index b44f1df013b2..feb9097c9881 100644
--- a/arch/x86/include/asm/tdx_global_metadata.h
+++ b/arch/x86/include/asm/tdx_global_metadata.h
@@ -34,11 +34,17 @@ struct tdx_sys_info_td_conf {
 	u64 cpuid_config_values[128][2];
 };
 
+struct tdx_sys_info_ext {
+	u16 memory_pool_required_pages;
+	u8 ext_required;
+};
+
 struct tdx_sys_info {
 	struct tdx_sys_info_features features;
 	struct tdx_sys_info_tdmr tdmr;
 	struct tdx_sys_info_td_ctrl td_ctrl;
 	struct tdx_sys_info_td_conf td_conf;
+	struct tdx_sys_info_ext ext;
 };
 
 #endif
diff --git a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
index c366bace454e..6835af65a5f8 100644
--- a/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
+++ b/arch/x86/virt/vmx/tdx/tdx_global_metadata.c
@@ -12,6 +12,7 @@ struct field_mapping {
 	int offset;
 	int size;
 	int count;
+	u64 feature0_mask;
 };
 
 /*
@@ -35,24 +36,28 @@ struct field_mapping {
 #define TD_SYSINFO_CHECK_SIZE(_field_id, _size)		\
 	__builtin_choose_expr(MD_FIELD_SIZE(_field_id) == (_size), _size, (void)0)
 
-#define _TD_SYSINFO_MAP(_field_id, _member, _count)			\
+#define _TD_SYSINFO_MAP(_field_id, _member, _count, _feature0_mask)	\
 	{ .field_id = _field_id,					\
 	  .offset = offsetof(struct tdx_sys_info, _member),		\
 	  .size = TD_SYSINFO_CHECK_SIZE(_field_id,			\
 					sizeof_field(struct tdx_sys_info, _member)), \
-	  .count = _count }
+	  .count = _count,						\
+	  .feature0_mask = _feature0_mask }
 
 #define TD_SYSINFO_MAP(_field_id, _member)				\
-	_TD_SYSINFO_MAP(_field_id, _member, 1)
+	_TD_SYSINFO_MAP(_field_id, _member, 1, 0)
 
 #define TD_SYSINFO_MAP_ARR(_field_id, _arr)				\
 	_TD_SYSINFO_MAP(_field_id, _arr[0],				\
-			ARRAY_SIZE(((struct tdx_sys_info *)0)->_arr))
+			ARRAY_SIZE(((struct tdx_sys_info *)0)->_arr), 0)
 
 #define TD_SYSINFO_MAP_2DARR(_field_id, _arr)				\
 	_TD_SYSINFO_MAP(_field_id, _arr[0][0],				\
 			ARRAY_SIZE(((struct tdx_sys_info *)0)->_arr) *	\
-			ARRAY_SIZE(((struct tdx_sys_info *)0)->_arr[0]))
+			ARRAY_SIZE(((struct tdx_sys_info *)0)->_arr[0]), 0)
+
+#define TD_SYSINFO_MAP_FEATURE0(_field_id, _member, _feature0_mask)	\
+	_TD_SYSINFO_MAP(_field_id, _member, 1, _feature0_mask)
 
 /* Map TD_SYSINFO fields into 'struct tdx_sys_info': */
 static const struct field_mapping mappings[] = {
@@ -76,6 +81,12 @@ static const struct field_mapping mappings[] = {
 	TD_SYSINFO_MAP(0x9900000100000008, td_conf.max_vcpus_per_td),
 	TD_SYSINFO_MAP_ARR(0x9900000300000400, td_conf.cpuid_config_leaves),
 	TD_SYSINFO_MAP_2DARR(0x9900000300000500, td_conf.cpuid_config_values),
+
+	TD_SYSINFO_MAP_FEATURE0(0x3100000100000000,
+				ext.memory_pool_required_pages,
+				TDX_FEATURES0_EXT),
+	TD_SYSINFO_MAP_FEATURE0(0x3100000000000001, ext.ext_required,
+				TDX_FEATURES0_EXT),
 };
 
 static int read_sys_metadata_field(const struct field_mapping *base,
@@ -83,6 +94,10 @@ static int read_sys_metadata_field(const struct field_mapping *base,
 {
 	int i, ret;
 
+	if (base->feature0_mask &&
+	    !(ts->features.tdx_features0 & base->feature0_mask))
+		return 0;
+
 	for (i = 0; i < base->count; i++) {
 		void *field = ((void *)ts) + base->offset + base->size * i;
 		u64 field_id = base->field_id + i;
-- 
2.25.1