x86/virt/tdx: Clarify try_init_module_global() result caching

TDX module global initialization is executed only once. The first call
caches both the return code and the "done" state in static function
variables.  Later callers read the variables. A lock protects the
saved state and serializes callers.

These variables will soon be moved to a global structure. Prepare for
that by treating the variables as a unit. Assign them together and
limit accesses to while the lock is held.

[ dhansen: mostly rewrite changelog ]

Signed-off-by: Chao Gao <chao.gao@intel.com>
Signed-off-by: Dave Hansen <dave.hansen@linux.intel.com>
Link: https://patch.msgid.link/20260520133909.409394-2-chao.gao@intel.com

diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c
index c0c6281b08a5e19d88d821373a40d3785028512f..ad56f142dd0bcc425046eb9d7078fef04df408da 100644 (file)
--- 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;
 }
 
 /**