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

[Joonas Lahtinen <joonas.lahtinen@linux.intel.com>]

On pe, 2015-08-28 at 15:41 +0800, Zhiyuan Lv wrote:
> 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>

Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.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;
>  
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