[PATCH v2 3/6] drm/i915: Always enable execlists on BDW for vgpu

[Zhiyuan Lv <zhiyuan.lv@intel.com>]

Broadwell hardware supports both ring buffer mode and execlist mode.
When i915 runs inside a VM with Intel GVT-g, we allow execlist mode
only.

The main reason of EXECLIST only is that GVT-g does not support the
dynamic mode switch between ring buffer mode and execlist mode when
running multiple virtual machines.

v2:
- Adjust the position of vgpu check in sanitize function (Joonas)
- Add vgpu error check in context initialization. (Joonas, Daniel)

Signed-off-by: Zhiyuan Lv <zhiyuan.lv@intel.com>
Signed-off-by: Zhi Wang <zhi.a.wang@intel.com>
---
 drivers/gpu/drm/i915/i915_gem_context.c | 7 +++++++
 drivers/gpu/drm/i915/intel_lrc.c        | 6 ++++++
 2 files changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_context.c b/drivers/gpu/drm/i915/i915_gem_context.c
index 8e893b3..74aa0c9 100644
--- a/drivers/gpu/drm/i915/i915_gem_context.c
+++ b/drivers/gpu/drm/i915/i915_gem_context.c
@@ -332,6 +332,13 @@ int i915_gem_context_init(struct drm_device *dev)
 	if (WARN_ON(dev_priv->ring[RCS].default_context))
 		return 0;
 
+	if (intel_vgpu_active(dev) && HAS_LOGICAL_RING_CONTEXTS(dev)) {
+		if (!i915.enable_execlists) {
+			DRM_INFO("Only EXECLIST mode is supported in vgpu.\n");
+			return -EINVAL;
+		}
+	}
+
 	if (i915.enable_execlists) {
 		/* NB: intentionally left blank. We will allocate our own
 		 * backing objects as we need them, thank you very much */
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 258af9b..e9520af 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -236,6 +236,12 @@ int intel_sanitize_enable_execlists(struct drm_device *dev, int enable_execlists
 {
 	WARN_ON(i915.enable_ppgtt == -1);
 
+	/* On platforms with execlist available, vGPU will only
+	 * support execlist mode, no ring buffer mode.
+	 */
+	if (HAS_LOGICAL_RING_CONTEXTS(dev) && intel_vgpu_active(dev))
+		return 1;
+
 	if (INTEL_INFO(dev)->gen >= 9)
 		return 1;
 
-- 
1.9.1

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