On 24/05/18 11:52, Mark Rutland wrote:

On Wed, May 23, 2018 at 10:23:20AM +0100, Julien Grall wrote:

quoted

Hi Marc,

On 05/22/2018 04:06 PM, Marc Zyngier wrote:

quoted

diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S
index ec2ee720e33e..f33e6aed3037 100644
--- a/arch/arm64/kernel/entry.S
+++ b/arch/arm64/kernel/entry.S

@@ -18,6 +18,7 @@
    * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    */
+#include <linux/arm-smccc.h>
   #include <linux/init.h>
   #include <linux/linkage.h>

@@ -137,6 +138,18 @@ alternative_else_nop_endif
   	add	\dst, \dst, #(\sym - .entry.tramp.text)
   	.endm
+	// This macro corrupts x0-x3. It is the caller's duty
+	// to save/restore them if required.

NIT: Shouldn't you use /* ... */ for multi-line comments?

There's no requirement to do so, and IIRC even Torvalds prefers '//'
comments for multi-line things these days.

Also, this is an assembly code, not C; '//' is the actual A64 assembler 
comment syntax so is arguably more appropriate here in spite of being 
moot thanks to preprocessing.

Robin.