[Intel-gfx] [PATCH] drm/i915: Fix EIO/wedged handling in gem fault handler

[Daniel Vetter]

In

commit 1f83fee08d625f8d0130f9fe5ef7b17c2e022f3c
Author: Daniel Vetter <daniel.vetter at ffwll.ch>
Date:   Thu Nov 15 17:17:22 2012 +0100

    drm/i915: clear up wedged transitions

I've accidentally inverted the EIO/wedged handling in the fault
handler: We want to return the EIO as a SIGBUS only if it's not
because of the gpu having died, to prevent userspace from unduly
dying.

In my defence the comment right above is completely misleading, so fix
both.

v2: Drop the WARN_ON, it's not actually a bug to e.g. receive an -EIO
when swap-in fails.

v3: Don't remove too much ... oops.

Reported-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: stable at vger.kernel.org
Signed-off-by: Daniel Vetter <daniel.vetter at intel.com>
---
 drivers/gpu/drm/i915/i915_gem.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 6c685708a516..4ca3a6dcf10b 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1596,10 +1596,13 @@ unlock:
 out:
 	switch (ret) {
 	case -EIO:
-		/* If this -EIO is due to a gpu hang, give the reset code a
-		 * chance to clean up the mess. Otherwise return the proper
-		 * SIGBUS. */
-		if (i915_terminally_wedged(&dev_priv->gpu_error)) {
+		/*
+		 * We eat errors when the gpu is terminally wedged to avoid
+		 * userspace unduly crashing (gl has no provisions for mmaps to
+		 * fail). But any other -EIO isn't ours (e.g. swap in failure)
+		 * and so needs to be reported.
+		 */
+		if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
 			ret = VM_FAULT_SIGBUS;
 			break;
 		}
-- 
2.0.1