[PATCH v2 7/7] PM / hibernate: Add minimal noinstr annotations

Peter Zijlstra
2023-01-16T14:52:43Z

When resuming there must not be any code between swsusp_arch_suspend()
and restore_processor_state() since the CPU state is ill defined at
this point in time.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
kernel/power/hibernate.c | 30 +++++++++++++++++++++++++++---
1 file changed, 27 insertions(+), 3 deletions(-)

--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -280,6 +280,32 @@ __weak int arch_resume_nosmt(void)
return 0;
}

+static noinstr int suspend_and_restore(void)
+{
+ int error;
+
+ /*
+ * Strictly speaking swsusp_arch_suspend() should be noinstr too but it
+ * is typically written in asm, as such, assume it is good and shut up
+ * the validator.
+ */
+ instrumentation_begin();
+ error = swsusp_arch_suspend();
+ instrumentation_end();
+
+ /*
+ * Architecture resume code 'returns' from the swsusp_arch_suspend()
+ * call and resumes execution here with some very dodgy machine state.
+ *
+ * Compiler instrumentation between these two calls (or in
+ * restore_processor_state() for that matter) will make life *very*
+ * interesting indeed.
+ */
+ restore_processor_state();
+
+ return error;
+}
+
/**
* create_image - Create a hibernation image.
* @platform_mode: Whether or not to use the platform driver.
@@ -323,9 +349,7 @@ static int create_image(int platform_mod
in_suspend = 1;
save_processor_state();
trace_suspend_resume(TPS("machine_suspend"), PM_EVENT_HIBERNATE, true);
- error = swsusp_arch_suspend();
- /* Restore control flow magically appears here */
- restore_processor_state();
+ error = suspend_and_restore();
trace_suspend_resume(TPS("machine_suspend"), PM_EVENT_HIBERNATE, false);
if (error)
pr_err("Error %d creating image\n", error);