[PATCH v8 05/21] x86/virt/seamldr: Add a helper to retrieve P-SEAMLDR information

Chao Gao
2026-04-27T15:30:00Z

P-SEAMLDR reports its state via SEAMLDR.INFO, including its version and
the number of remaining runtime updates.

This information is useful for userspace. For example, the admin can use
the P-SEAMLDR version to determine whether a candidate TDX module is
compatible with the running loader, and can use the remaining update count
to determine whether another runtime update is still possible.

Add a helper to retrieve P-SEAMLDR information in preparation for
exposing P-SEAMLDR version and other necessary information to userspace.
Export the new kAPI for use by tdx-host.ko.

Note that there are two distinct P-SEAMLDR APIs with similar names:

SEAMLDR.INFO: Returns a SEAMLDR_INFO structure containing SEAMLDR
information such as version and remaining updates.

SEAMLDR.SEAMINFO: Returns a SEAMLDR_SEAMINFO structure containing SEAM
and system information such as Convertible Memory
Regions (CMRs) and number of CPUs and sockets.

The former is used here.

For details, see "Intel® Trust Domain Extensions - SEAM Loader (SEAMLDR)
Interface Specification".

Signed-off-by: Chao Gao <chao.gao@intel.com>
Reviewed-by: Kai Huang <kai.huang@intel.com>
Reviewed-by: Kiryl Shutsemau (Meta) <kas@kernel.org>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Reviewed-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
---
arch/x86/include/asm/seamldr.h | 36 +++++++++++++++++++++++++++++++++
arch/x86/virt/vmx/tdx/seamldr.c | 20 +++++++++++++++++-
2 files changed, 55 insertions(+), 1 deletion(-)
create mode 100644 arch/x86/include/asm/seamldr.h

diff --git a/arch/x86/include/asm/seamldr.h b/arch/x86/include/asm/seamldr.h
new file mode 100644
index 000000000000..c67e5bc910a9
--- /dev/null
+++ b/arch/x86/include/asm/seamldr.h
@@ -0,0 +1,36 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SEAMLDR_H
+#define _ASM_X86_SEAMLDR_H
+
+#include <linux/types.h>
+
+/*
+ * This is called the "SEAMLDR_INFO" data structure and is defined
+ * in "SEAM Loader (SEAMLDR) Interface Specification".
+ *
+ * The SEAMLDR.INFO documentation requires this to be aligned to a
+ * 256-byte boundary.
+ */
+struct seamldr_info {
+ u32 version;
+ u32 attributes;
+ u32 vendor_id;
+ u32 build_date;
+ u16 build_num;
+ u16 minor_version;
+ u16 major_version;
+ u16 update_version;
+ u32 acm_x2apicid;
+ u32 num_remaining_updates;
+ u8 seam_info[128];
+ u8 seam_ready;
+ u8 seam_debug;
+ u8 p_seam_ready;
+ u8 reserved[93];
+} __packed __aligned(256);
+
+static_assert(sizeof(struct seamldr_info) == 256);
+
+int seamldr_get_info(struct seamldr_info *seamldr_info);
+
+#endif /* _ASM_X86_SEAMLDR_H */
diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index 65616dd2f4d2..7269a239bc22 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -8,8 +8,13 @@

#include <linux/spinlock.h>

+#include <asm/seamldr.h>
+
#include "seamcall_internal.h"

+/* P-SEAMLDR SEAMCALL leaf function */
+#define P_SEAMLDR_INFO 0x8000000000000000
+
/*
* Serialize P-SEAMLDR calls since the hardware only allows a single CPU to
* interact with P-SEAMLDR simultaneously. Use raw version as the calls can
@@ -18,8 +23,21 @@
*/
static DEFINE_RAW_SPINLOCK(seamldr_lock);

-static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
+static int seamldr_call(u64 fn, struct tdx_module_args *args)
{
guard(raw_spinlock)(&seamldr_lock);
return seamcall_prerr(fn, args);
}
+
+int seamldr_get_info(struct seamldr_info *seamldr_info)
+{
+ struct tdx_module_args args = {};
+
+ /*
+ * Use slow_virt_to_phys() since @seamldr_info may be allocated on
+ * the stack.
+ */
+ args.rcx = slow_virt_to_phys(seamldr_info);
+ return seamldr_call(P_SEAMLDR_INFO, &args);
+}
+EXPORT_SYMBOL_FOR_MODULES(seamldr_get_info, "tdx-host");
--
2.47.1