[4.2.y-ckt stable] Patch "drm/i915: Restore inhibiting the load of the default context" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

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

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 2cfe41af1ab095c0f9200821ebb06cb869aa9fbd Mon Sep 17 00:00:00 2001
From: Chris Wilson <chris at chris-wilson.co.uk>
Date: Fri, 27 Nov 2015 13:28:55 +0000
Subject: drm/i915: Restore inhibiting the load of the default context

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 <benjamin.widawsky at intel.com>
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.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Michel Thierry <michel.thierry at intel.com>
Cc: Mika Kuoppala <mika.kuoppala at intel.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Link: http://patchwork.freedesktop.org/patch/msgid/1448630935-27377-1-git-send-email-chris@chris-wilson.co.uk
Reviewed-by: Mika Kuoppala <mika.kuoppala at intel.com>
[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.]
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
(cherry picked from commit 42f1cae8c079bcceb3cff079fddc3ff8852c788f)
Signed-off-by: Jani Nikula <jani.nikula at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 48afa77..2d96da6 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -317,6 +317,10 @@ void i915_gem_context_reset(struct drm_device *dev)
 			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;
 	}
 }

@@ -685,7 +689,7 @@ static int do_switch(struct intel_engine_cs *ring,
 	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
--
1.9.1