[Intel-gfx] [PATCH] drm/i915: Add missed MI_BATCH_BUFFER_END in null state batch buffer.

[Zhi Wang]

Currently MI_BATCH_BUFFER_END is missed in null state batch buffer.
This fix is trying to append the missed instruction at the end of
null state batch buffer gem bo after it was initialized and filled
with null state commands.

This issue was exposed under full GPU virtualization(Intel GVT-g) environment.

Signed-off-by: Zhi Wang <zhi.a.wang at intel.com>
---
 drivers/gpu/drm/i915/i915_gem_render_state.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/i915/i915_gem_render_state.c b/drivers/gpu/drm/i915/i915_gem_render_state.c
index 98dcd94..3495b4b 100644
--- a/drivers/gpu/drm/i915/i915_gem_render_state.c
+++ b/drivers/gpu/drm/i915/i915_gem_render_state.c
@@ -54,7 +54,8 @@ static int render_state_init(struct render_state *so, struct drm_device *dev)
 	if (so->rodata == NULL)
 		return 0;
 
-	if (so->rodata->batch_items * 4 > 4096)
+	/* Leave one dword for MI_BATCH_BUFFER_END. */
+	if ((so->rodata->batch_items * 4 + 1) > 4096)
 		return -EINVAL;
 
 	so->obj = i915_gem_alloc_object(dev, 4096);
@@ -108,6 +109,7 @@ static int render_state_setup(struct render_state *so)
 
 		d[i++] = s;
 	}
+	d[i] = MI_BATCH_BUFFER_END;
 	kunmap(page);
 
 	ret = i915_gem_object_set_to_gtt_domain(so->obj, false);
-- 
1.8.3.2