drm/i915: fix blank screen booting crashes

5.15-rc1 crashes with blank screen when booting up on two ThinkPads
using i915.  Bisections converge convincingly, but arrive at different
and suprising "culprits", none of them the actual culprit.

netconsole (with init_netconsole() hacked to call i915_init() when
logging has started, instead of by module_init()) tells the story:

kernel BUG at drivers/gpu/drm/i915/i915_sw_fence.c:245!
with RSI: ffffffff814d408b pointing to sw_fence_dummy_notify().
I've been building with CONFIG_CC_OPTIMIZE_FOR_SIZE=y, and that
function needs to be 4-byte aligned.

Fixes: 62eaf0a ("drm/i915/guc: Support request cancellation")
Signed-off-by: Hugh Dickins <[email protected]>
Tested-by: Steven Rostedt (VMware) <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

Author: Hugh Dickins

drivers/gpu/drm/i915/gt/intel_context.c

@@ -362,8 +362,9 @@ static int __intel_context_active(struct i915_active *active)
 	return 0;
 }
 
-static int sw_fence_dummy_notify(struct i915_sw_fence *sf,
-				 enum i915_sw_fence_notify state)
+static int __i915_sw_fence_call
+sw_fence_dummy_notify(struct i915_sw_fence *sf,
+		      enum i915_sw_fence_notify state)
 {
 	return NOTIFY_DONE;
 }