Patch "drm/i915: Restore inhibiting the load of the default context" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

drm/i915: Restore inhibiting the load of the default context

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
drm-i915-restore-inhibiting-the-load-of-the-default-context.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Chris Wilson <[email protected]>
Date: Fri, 27 Nov 2015 13:28:55 +0000
Subject: drm/i915: Restore inhibiting the load of the default context

From: Chris Wilson <[email protected]>

commit 06ef83a705a98da63797a5a570220b6ca36febd4 upstream.

Following a GPU reset, we may leave the context in a poorly defined state, and reloading from that context will leave the GPU flummoxed. For secondary contexts, this will lead to that context being banned - but currently it is also causing the default context to become banned, leading to turmoil in the shared state.

This is a regression from

commit 6702cf16e0ba8b0129f5aa1b6609d4e9c70bc13b [v4.1]

Author: Ben Widawsky <[email protected]>
Date:   Mon Mar 16 16:00:58 2015 +0000

drm/i915: Initialize all contexts

which quietly introduced the removal of the MI_RESTORE_INHIBIT on the default context.

v2: Mark the global default context as uninitialized on GPU reset so that the context-local workarounds are reloaded upon re-enabling.

[danvet: This seems to fix a gpu hand on after the first resume, resulting in any future suspend operation failing with -EIO because the gpu seems to be in a funky state. Somehow this patch fixes that.]

---
 drivers/gpu/drm/i915/i915_gem_context.c |    6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

@@ -340,6 +340,10 @@ void i915_gem_context_reset(struct drm_d
 			i915_gem_context_unreference(lctx);
 			ring->last_context = NULL;
 		}
+
+		/* Force the GPU state to be reinitialised on enabling */
+		if (ring->default_context)
+			ring->default_context->legacy_hw_ctx.initialized = false;
 	}
 }
 

@@ -708,7 +712,7 @@ static int do_switch(struct drm_i915_gem
 	if (ret)
 		goto unpin_out;
 
-	if (!to->legacy_hw_ctx.initialized) {
+	if (!to->legacy_hw_ctx.initialized || i915_gem_context_is_default(to)) {
 		hw_flags |= MI_RESTORE_INHIBIT;
 		/* NB: If we inhibit the restore, the context is not allowed to
 		 * die because future work may end up depending on valid address

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/drm-i915-init-power-domains-early-in-driver-load.patch queue-4.4/drm-i915-restore-inhibiting-the-load-of-the-default-context.patch