x86/stackprotector: Move __stack_chk_guard to percpu hot section

No functional change.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Uros Bizjak <ubizjak@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: https://lore.kernel.org/r/20250303165246.2175811-11-brgerst@gmail.com

arch/x86/include/asm/stackprotector.h

@@ -20,7 +20,7 @@
 
 #include <linux/sched.h>
 
-DECLARE_PER_CPU(unsigned long, __stack_chk_guard);
+DECLARE_PER_CPU_CACHE_HOT(unsigned long, __stack_chk_guard);
 
 /*
  * Initialize the stackprotector canary value.

arch/x86/kernel/cpu/common.c

@@ -2147,7 +2147,7 @@ void syscall_init(void)
 #endif /* CONFIG_X86_64 */
 
 #ifdef CONFIG_STACKPROTECTOR
-DEFINE_PER_CPU(unsigned long, __stack_chk_guard);
+DEFINE_PER_CPU_CACHE_HOT(unsigned long, __stack_chk_guard);
 #ifndef CONFIG_SMP
 EXPORT_PER_CPU_SYMBOL(__stack_chk_guard);
 #endif