[PATCH v10 01/25] x86/virt/tdx: Clarify try_init_module_global() result caching

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

TDX module global initialization is executed only once. The first call
caches both the result and the "done" state, and later callers reuse the
saved result. A lock protects that cached state.

The current code is hard to read because sysinit_done is accessed under
the lock, while sysinit_ret is not.

To improve readability, move sysinit_ret accesses within the lock.

Group sysinit_ret/sysinit_done updates right after initialization so
Caching the result is separate from the initialization itself.

Signed-off-by: Chao Gao <chao.gao@intel.com>
---
 arch/x86/virt/vmx/tdx/tdx.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index c0c6281b08a5..ad56f142dd0b 100644
--- a/arch/x86/virt/vmx/tdx/tdx.c
+++ b/arch/x86/virt/vmx/tdx/tdx.c
@@ -115,28 +115,34 @@ static int try_init_module_global(void)
 	static DEFINE_RAW_SPINLOCK(sysinit_lock);
 	static bool sysinit_done;
 	static int sysinit_ret;
+	int ret;
 
 	raw_spin_lock(&sysinit_lock);
 
-	if (sysinit_done)
+	/* Return the "cached" return code. */
+	if (sysinit_done) {
+		ret = sysinit_ret;
 		goto out;
+	}
 
 	/* RCX is module attributes and all bits are reserved */
 	args.rcx = 0;
-	sysinit_ret = seamcall_prerr(TDH_SYS_INIT, &args);
+	ret = seamcall_prerr(TDH_SYS_INIT, &args);
 
 	/*
 	 * The first SEAMCALL also detects the TDX module, thus
 	 * it can fail due to the TDX module is not loaded.
 	 * Dump message to let the user know.
 	 */
-	if (sysinit_ret == -ENODEV)
+	if (ret == -ENODEV)
 		pr_err("module not loaded\n");
 
+	/* Save the return code for later callers. */
 	sysinit_done = true;
+	sysinit_ret = ret;
 out:
 	raw_spin_unlock(&sysinit_lock);
-	return sysinit_ret;
+	return ret;
 }
 
 /**
-- 
2.52.0