[PATCH 5/5] x86/virt/tdx: Export global metadata read infrastructure

[Kai Huang <kai.huang@intel.com>]

KVM will need to read a bunch of non-TDMR related metadata to create and
run TDX guests.  Export the metadata read infrastructure for KVM to use.

Specifically, export two helpers:

1) The helper which reads multiple metadata fields to a buffer of a
   structure based on the "field ID -> structure member" mapping table.

2) The low level helper which just reads a given field ID.

The two helpers cover cases when the user wants to cache a bunch of
metadata fields to a certain structure and when the user just wants to
query a specific metadata field on demand.  They are enough for KVM to
use (and also should be enough for other potential users).

Signed-off-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
 arch/x86/include/asm/tdx.h  | 22 ++++++++++++++++++++++
 arch/x86/virt/vmx/tdx/tdx.c | 25 ++++++++-----------------
 2 files changed, 30 insertions(+), 17 deletions(-)

diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h
index eba178996d84..709b9483f9e4 100644
--- a/arch/x86/include/asm/tdx.h
+++ b/arch/x86/include/asm/tdx.h
@@ -116,6 +116,28 @@ static inline u64 sc_retry(sc_func_t func, u64 fn,
 int tdx_cpu_enable(void);
 int tdx_enable(void);
 const char *tdx_dump_mce_info(struct mce *m);
+
+struct tdx_metadata_field_mapping {
+	u64 field_id;
+	int offset;
+	int size;
+};
+
+#define TD_SYSINFO_MAP(_field_id, _struct, _member)	\
+	{ .field_id = MD_FIELD_ID_##_field_id,		\
+	  .offset   = offsetof(_struct, _member),	\
+	  .size     = sizeof(typeof(((_struct *)0)->_member)) }
+
+/*
+ * Read multiple global metadata fields to a buffer of a structure
+ * based on the "field ID -> structure member" mapping table.
+ */
+int tdx_sys_metadata_read(const struct tdx_metadata_field_mapping *fields,
+			  int nr_fields, void *stbuf);
+
+/* Read a single global metadata field */
+int tdx_sys_metadata_field_read(u64 field_id, u64 *data);
+
 #else
 static inline void tdx_init(void) { }
 static inline int tdx_cpu_enable(void) { return -ENODEV; }
diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 4ee4b8cf377c..dc21310776ab 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -251,7 +251,7 @@ static int build_tdx_memlist(struct list_head *tmb_list)
 	return ret;
 }
 
-static int read_sys_metadata_field(u64 field_id, u64 *data)
+int tdx_sys_metadata_field_read(u64 field_id, u64 *data)
 {
 	struct tdx_module_args args = {};
 	int ret;
@@ -270,6 +270,7 @@ static int read_sys_metadata_field(u64 field_id, u64 *data)
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(tdx_sys_metadata_field_read);
 
 /* Return the metadata field element size in bytes */
 static int get_metadata_field_bytes(u64 field_id)
@@ -295,7 +296,7 @@ static int stbuf_read_sys_metadata_field(u64 field_id,
 	if (WARN_ON_ONCE(get_metadata_field_bytes(field_id) != bytes))
 		return -EINVAL;
 
-	ret = read_sys_metadata_field(field_id, &tmp);
+	ret = tdx_sys_metadata_field_read(field_id, &tmp);
 	if (ret)
 		return ret;
 
@@ -304,19 +305,8 @@ static int stbuf_read_sys_metadata_field(u64 field_id,
 	return 0;
 }
 
-struct field_mapping {
-	u64 field_id;
-	int offset;
-	int size;
-};
-
-#define TD_SYSINFO_MAP(_field_id, _struct, _member)	\
-	{ .field_id = MD_FIELD_ID_##_field_id,		\
-	  .offset   = offsetof(_struct, _member),	\
-	  .size     = sizeof(typeof(((_struct *)0)->_member)) }
-
-static int read_sys_metadata(const struct field_mapping *fields, int nr_fields,
-			     void *stbuf)
+int tdx_sys_metadata_read(const struct tdx_metadata_field_mapping *fields,
+			  int nr_fields, void *stbuf)
 {
 	int i, ret;
 
@@ -331,6 +321,7 @@ static int read_sys_metadata(const struct field_mapping *fields, int nr_fields,
 
 	return 0;
 }
+EXPORT_SYMBOL_GPL(tdx_sys_metadata_read);
 
 #define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member)	\
 	TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
@@ -338,7 +329,7 @@ static int read_sys_metadata(const struct field_mapping *fields, int nr_fields,
 static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
 {
 	/* Map TD_SYSINFO fields into 'struct tdx_tdmr_sysinfo': */
-	const struct field_mapping fields[] = {
+	const struct tdx_metadata_field_mapping fields[] = {
 		TD_SYSINFO_MAP_TDMR_INFO(MAX_TDMRS,		max_tdmrs),
 		TD_SYSINFO_MAP_TDMR_INFO(MAX_RESERVED_PER_TDMR, max_reserved_per_tdmr),
 		TD_SYSINFO_MAP_TDMR_INFO(PAMT_4K_ENTRY_SIZE,    pamt_entry_size[TDX_PS_4K]),
@@ -347,7 +338,7 @@ static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)
 	};
 
 	/* Populate 'tdmr_sysinfo' fields using the mapping structure above: */
-	return read_sys_metadata(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
+	return tdx_sys_metadata_read(fields, ARRAY_SIZE(fields), tdmr_sysinfo);
 }
 
 /* Calculate the actual TDMR size */
-- 
2.43.2