[RFC PATCH 06/20] x86/virt/seamldr: Add a helper to read P-SEAMLDR information

[Chao Gao <chao.gao@intel.com>]

Add a helper function to retrieve P-SEAMLDR information, including its
version and features, using the dedicated P_SEAMLDR_INFO API. This is in
preparation for exposing this information to userspace. Userspace will
utilize the version number to verify the compatibility of TDX modules
with the P-SEAMLDR

Signed-off-by: Chao Gao <chao.gao@intel.com>
Tested-by: Farrah Chen <farrah.chen@intel.com>
---
 arch/x86/virt/vmx/tdx/seamldr.c | 28 +++++++++++++++++++++++++++-
 1 file changed, 27 insertions(+), 1 deletion(-)

diff --git a/arch/x86/virt/vmx/tdx/seamldr.c b/arch/x86/virt/vmx/tdx/seamldr.c
index a252f1ae3483..c2771323729c 100644
--- a/arch/x86/virt/vmx/tdx/seamldr.c
+++ b/arch/x86/virt/vmx/tdx/seamldr.c
@@ -11,7 +11,26 @@
 #include "tdx.h"
 #include "../vmx.h"
 
-static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
+ /* P-SEAMLDR SEAMCALL leaf function */
+#define P_SEAMLDR_INFO			0x8000000000000000
+
+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;
+	u8	reserved0[4];
+	u32	num_remaining_updates;
+	u8	reserved1[224];
+} __packed;
+
+static struct seamldr_info seamldr_info __aligned(256);
+
+static inline int seamldr_call(u64 fn, struct tdx_module_args *args)
 {
 	u64 vmcs;
 	int ret;
@@ -42,3 +61,10 @@ static __maybe_unused int seamldr_call(u64 fn, struct tdx_module_args *args)
 
 	return ret;
 }
+
+static __maybe_unused int get_seamldr_info(void)
+{
+	struct tdx_module_args args = { .rcx = __pa(&seamldr_info) };
+
+	return seamldr_call(P_SEAMLDR_INFO, &args);
+}
-- 
2.47.1