Re: [PATCH v9 2/3] drm/i915: Enable guest i915 full ppgtt functionality

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

On to, 2017-08-10 at 07:41 +0800, Tina Zhang wrote:
> Enable the guest i915 full ppgtt functionality when host can provide this
> capability. vgt_caps is introduced to guest i915 driver to get the vgpu
> capabilities from the device model. VGT_CPAS_FULL_PPGTT is one of the
> capabilities type to let guest i915 dirver know that the guest i915 full
> ppgtt is supported by device model.
> 
> Notice that the minor version of pvinfo isn't bumped because of this
> vgt_caps introduction, due to older guest would be broken by simply
> increasing the pvinfo version. Although the pvinfo minor version doesn't
> increase, the compatibility won't be blocked. The compatibility is ensured
> by checking the value of caps field in pvinfo. Zero means no full ppgtt
> support and BIT(2) means this feature is provided.
> 
> Changes since v1:
> - Use u32 instead of uint32_t (Joonas)
> - Move VGT_CAPS_FULL_PPGTT introduction to this patch and use #define
>   instead of enum (Joonas)
> - Rewrite the vgpu full ppgtt capability checking logic. (Joonas)
> - Some coding style refine. (Joonas)
> 
> Changes since v2:
> - Divide the whole patch set into two separate patch series, with one
>   patch in i915 side to check guest i915 full ppgtt capability and enable
>   it when this capability is supported by the device model, and the other
>   one in gvt side which fixs the blocking issue and enables the device
>   model to provide the capability to guest. And this patch focuses on guest
>   i915 side. (Joonas)
> - Change the title from "introduce vgt_caps to pvinfo" to
>   "Enable guest i915 full ppgtt functionality". (Tina)
> 
> Change since v3:
> - Add some comments about pvinfo caps and version. (Joonas)
> 
> Change since v4:
> - Tested by Tina Zhang.
> 
> Change since v5:
> - Add limitation about supporting 32bit full ppgtt.
> 
> Change since v6:
> - Change the fallback to 48bit full ppgtt if i915.ppgtt_enable=2. (Zhenyu)
> 
> Change in v9:
> - Remove the fixme comment due to no plan for 32bit full ppgtt
>   support. (Zhenyu)
> - Reorder the patch-set to fix compiling issue with git-bisect. (Zhenyu)
> - Add print log when forcing guest 48bit full ppgtt. (Zhenyu)
> 
> Reviewed-by: Joonas Lahtinen <joonas.lahtinen@linux.intel.com> in v2
> Signed-off-by: Tina Zhang <tina.zhang@intel.com>

<SNIP>

> @@ -141,14 +141,19 @@ int intel_sanitize_enable_ppgtt(struct drm_i915_private *dev_priv,
>  
>  	has_aliasing_ppgtt = dev_priv->info.has_aliasing_ppgtt;
>  	has_full_ppgtt = dev_priv->info.has_full_ppgtt;
> -	has_full_48bit_ppgtt = dev_priv->info.has_full_48bit_ppgtt;

	Leave above line.

>  
>  	if (intel_vgpu_active(dev_priv)) {
> -		/* emulation is too hard */
> -		has_full_ppgtt = false;
> -		has_full_48bit_ppgtt = false;

		has_full_ppgtt = false;
		has_full_48bit_ppgtt =
			intel_vgpu_has_full_48bit_ppgtt(dev_priv);

> +		has_full_ppgtt = intel_vgpu_has_full_ppgtt(dev_priv);
> +		/* GVT-g has no support for 32bit ppgtt */
> +		if (enable_ppgtt == 2 && has_full_ppgtt) {
> +			DRM_DEBUG_DRIVER("Force 48bit ppgtt for vGPU\n");
> +			enable_ppgtt = 3;

Lets not do an upgrade for the user if they explicitly requested lower
level. I'd just leave the option to be and it'll get downgraded to
aliasing ppgtt.

> +		}
>  	}
>  
> +	has_full_48bit_ppgtt = has_full_ppgtt &&
> +		dev_priv->info.has_full_48bit_ppgtt;
> +

This can then be dropped too.

I'll send a patch to disconnect the has_full_ppgtt and
has_full_48bit_ppgtt flags.


>  	if (!has_aliasing_ppgtt)
>  		return 0;
>  
> @@ -49,12 +49,18 @@ enum vgt_g2v_type {
> >  	VGT_G2V_MAX,
>  };
>  
> +/*
> + * VGT capabilities type
> + */
> +#define VGT_CAPS_FULL_PPGTT_48BIT	BIT(2)

VGT_CAPS_FULL_48BIT_PPGTT for consistency

> @@ -75,10 +75,17 @@ void i915_check_vgpu(struct drm_i915_private *dev_priv)
>  		return;
>  	}
>  
> +	dev_priv->vgpu.caps = __raw_i915_read32(dev_priv, vgtif_reg(vgt_caps));
> +
>  	dev_priv->vgpu.active = true;
>  	DRM_INFO("Virtual GPU for Intel GVT-g detected.\n");
>  }
>  
> +bool intel_vgpu_has_full_ppgtt(struct drm_i915_private *dev_priv)

This should really be has_full_48bit_ppgtt() too.

Regards, Joonas
-- 
Joonas Lahtinen
Open Source Technology Center
Intel Corporation
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