[PATCH 4.9 10/44] arm64: Clear OSDLR_EL1 on CPU boot

[Greg Kroah-Hartman]

From: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com>

commit 6fda41bf12615ee7c3ddac88155099b1a8cf8d00 upstream.

Some firmwares may reboot CPUs with OS Double Lock set. Make sure that
it is unlocked, in order to use debug exceptions.

Cc: <sta...@vger.kernel.org>
Signed-off-by: Jean-Philippe Brucker <jean-philippe.bruc...@arm.com>
Signed-off-by: Will Deacon <will.dea...@arm.com>
Signed-off-by: Greg Kroah-Hartman <gre...@linuxfoundation.org>

---
 arch/arm64/kernel/debug-monitors.c |    1 +
 1 file changed, 1 insertion(+)

--- a/arch/arm64/kernel/debug-monitors.c
+++ b/arch/arm64/kernel/debug-monitors.c
@@ -132,6 +132,7 @@ NOKPROBE_SYMBOL(disable_debug_monitors);
  */
 static int clear_os_lock(unsigned int cpu)
 {
+       write_sysreg(0, osdlr_el1);
        write_sysreg(0, oslar_el1);
        isb();
        return 0;