[MIPS] Enable support for the userlocal hardware register

Which will cut down the cost of RDHWR $29 which is used to obtain the
TLS pointer and so far being emulated in software down to a single cycle
operation.

Signed-off-by: Ralf Baechle <ralf@linux-mips.org>

1 files changed, 2 insertions, 3 deletions

diff --git a/arch/mips/kernel/syscall.c b/arch/mips/kernel/syscall.c
index 9dd5a2df8ea..b947c61c0cc 100644
--- a/arch/mips/kernel/syscall.c
+++ b/arch/mips/kernel/syscall.c
@@ -272,9 +272,8 @@ asmlinkage int sys_set_thread_area(unsigned long addr)
 	struct thread_info *ti = task_thread_info(current);
 
 	ti->tp_value = addr;
-
-	/* If some future MIPS implementation has this register in hardware,
-	 * we will need to update it here (and in context switches).  */
+	if (cpu_has_userlocal)
+		write_c0_userlocal(addr);
 
 	return 0;
 }