[PATCH 3/9] x86/virt/tdx: Support global metadata read for all element sizes

Kai Huang
2024-06-16T12:01:53Z

The TDX module provides "global metadata fields" for software to query.
Each metadata field is accessible by a unique "metadata field ID". TDX
supports 8/16/32/64 bits metadata element sizes. The size of each
metadata field is encoded in its associated metadata field ID.

For now the kernel only reads "TD Memory Region" (TDMR) related global
metadata fields for module initialization. All these metadata fields
are 16-bit, and the kernel only supports reading 16-bit fields.

Future changes will need to read more metadata fields with other element
sizes. To resolve this once for all, extend the existing metadata
reading code to support reading all element sizes.

Signed-off-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.com>
---
arch/x86/virt/vmx/tdx/tdx.c | 29 ++++++++++++++++-------------
arch/x86/virt/vmx/tdx/tdx.h | 3 ++-
2 files changed, 18 insertions(+), 14 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index 854312e97eff..4392e82a9bcb 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -270,23 +270,25 @@ static int read_sys_metadata_field(u64 field_id, u64 *data)
return 0;
}

-static int read_sys_metadata_field16(u64 field_id,
- int offset,
- void *stbuf)
+/*
+ * Read one global metadata field and store the data to a location of a
+ * given buffer specified by the offset and size (in bytes).
+ */
+static int stbuf_read_sysmd_field(u64 field_id, void *stbuf, int offset,
+ int bytes)
{
- u16 *st_member = stbuf + offset;
+ void *st_member = stbuf + offset;
u64 tmp;
int ret;

- if (WARN_ON_ONCE(MD_FIELD_ID_ELE_SIZE_CODE(field_id) !=
- MD_FIELD_ID_ELE_SIZE_16BIT))
+ if (WARN_ON_ONCE(MD_FIELD_BYTES(field_id) != bytes))
return -EINVAL;

ret = read_sys_metadata_field(field_id, &tmp);
if (ret)
return ret;

- *st_member = tmp;
+ memcpy(st_member, &tmp, bytes);

return 0;
}
@@ -294,11 +296,13 @@ static int read_sys_metadata_field16(u64 field_id,
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) }
+#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)) }

#define TD_SYSINFO_MAP_TDMR_INFO(_field_id, _member) \
TD_SYSINFO_MAP(_field_id, struct tdx_tdmr_sysinfo, _member)
@@ -319,9 +323,8 @@ static int get_tdx_tdmr_sysinfo(struct tdx_tdmr_sysinfo *tdmr_sysinfo)

/* Populate 'tdmr_sysinfo' fields using the mapping structure above: */
for (i = 0; i < ARRAY_SIZE(fields); i++) {
- ret = read_sys_metadata_field16(fields[i].field_id,
- fields[i].offset,
- tdmr_sysinfo);
+ ret = stbuf_read_sysmd_field(fields[i].field_id, tdmr_sysinfo,
+ fields[i].offset, fields[i].size);
if (ret)
return ret;
}
diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h
index b701f69485d3..812943516946 100644
--- a/arch/x86/virt/vmx/tdx/tdx.h
+++ b/arch/x86/virt/vmx/tdx/tdx.h
@@ -53,7 +53,8 @@
#define MD_FIELD_ID_ELE_SIZE_CODE(_field_id) \
(((_field_id) & GENMASK_ULL(33, 32)) >> 32)

-#define MD_FIELD_ID_ELE_SIZE_16BIT 1
+#define MD_FIELD_BYTES(_field_id) \
+ (1 << MD_FIELD_ID_ELE_SIZE_CODE(_field_id))

struct tdmr_reserved_area {
u64 offset;
--
2.43.2