[tip: x86/tdx] x86/virt/seamldr: Add a helper to retrieve P-SEAMLDR information

["tip-bot2 for Chao Gao" <tip-bot2@linutronix.de>]

The following commit has been merged into the x86/tdx branch of tip:

Commit-ID:     fcbc30f0d66fed9a484a723d22702e704b02656c
Gitweb:        https://git.kernel.org/tip/fcbc30f0d66fed9a484a723d22702e704b02656c
Author:        Chao Gao <chao.gao@intel.com>
AuthorDate:    Wed, 20 May 2026 15:28:56 -07:00
Committer:     Dave Hansen <dave.hansen@linux.intel.com>
CommitterDate: Wed, 20 May 2026 15:37:09 -07:00

x86/virt/seamldr: Add a helper to retrieve P-SEAMLDR information

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, userspace 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 the "tdx_host" device.

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

  "SEAMLDR.INFO" is metadata about the loader. It's metadata for the
  update process.

  "SEAMLDR.SEAMINFO" is metadata about SEAM mode. It is for the module
  init process, not for the update process.

Use SEAMLDR.INFO here.

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

Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.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>
Reviewed-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260520133909.409394-10-chao.gao@intel.com
Link: https://patch.msgid.link/20260520222856.F362C738@davehans-spike.ostc.intel.com
---
 arch/x86/include/asm/seamldr.h  | 35 ++++++++++++++++++++++++++++++++-
 arch/x86/virt/vmx/tdx/seamldr.c | 20 +++++++++++++++++-
 2 files changed, 54 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 0000000..a74151b
--- /dev/null
+++ b/arch/x86/include/asm/seamldr.h
@@ -0,0 +1,35 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _ASM_X86_SEAMLDR_H
+#define _ASM_X86_SEAMLDR_H
+
+#include <linux/types.h>
+
+/*
+ * This is the "SEAMLDR_INFO" data structure defined in the
+ * "SEAM Loader (SEAMLDR) Interface Specification".
+ *
+ * Must 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 65616dd..7269a23 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");