FAILED: patch "[PATCH] drm/i915/gt: Prevent use of engine->wa_ctx after error" failed to apply to 4.19-stable tree

The patch below does not apply to the 4.19-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 488751a0ef9b5ce572c47301ce62d54fc6b5a74d Mon Sep 17 00:00:00 2001
From: Chris Wilson <[email protected]>
Date: Mon, 18 Jan 2021 09:53:32 +0000
Subject: [PATCH] drm/i915/gt: Prevent use of engine->wa_ctx after error

On error we unpin and free the wa_ctx.vma, but do not clear any of the derived flags. During lrc_init, we look at the flags and attempt to dereference the wa_ctx.vma if they are set. To protect the error path where we try to limp along without the wa_ctx, make sure we clear those flags!

(cherry-picked from 5b4dc95cf7f573e927fbbd406ebe54225d41b9b2)

index 7614a3d24fca..26c7d0a50585 100644
@@ -3988,6 +3988,9 @@ static int lrc_setup_wa_ctx(struct intel_engine_cs *engine)
 static void lrc_destroy_wa_ctx(struct intel_engine_cs *engine)
 {
 	i915_vma_unpin_and_release(&engine->wa_ctx.vma, 0);
+
+	/* Called on error unwind, clear all flags to prevent further use */
+	memset(&engine->wa_ctx, 0, sizeof(engine->wa_ctx));
 }
 
 typedef u32 *(*wa_bb_func_t)(struct intel_engine_cs *engine, u32 *batch);