[Intel-gfx] [PATCH v8 6/8] drm/i915: create context image vma in kernel context

[Michel Thierry]

Hi,

On 5/29/2018 12:16 PM, Lionel Landwerlin wrote:
> We want to be able to modify other context images from the kernel
> context in a following commit. To be able to do this we need to map
> the context image into the kernel context's ppgtt.
> 
> Signed-off-by: Lionel Landwerlin <lionel.g.landwerlin at intel.com>
> ---
>   drivers/gpu/drm/i915/i915_gem_context.h |  1 +
>   drivers/gpu/drm/i915/intel_lrc.c        | 19 ++++++++++++++-----
>   2 files changed, 15 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/gpu/drm/i915/i915_gem_context.h b/drivers/gpu/drm/i915/i915_gem_context.h
> index f40d85448a28..9c313c2edb09 100644
> --- a/drivers/gpu/drm/i915/i915_gem_context.h
> +++ b/drivers/gpu/drm/i915/i915_gem_context.h
> @@ -155,6 +155,7 @@ struct i915_gem_context {
>   	struct intel_context {
>   		struct i915_gem_context *gem_context;
>   		struct i915_vma *state;
> +		struct i915_vma *kernel_state; /**/
>   		struct intel_ring *ring;
>   		u32 *lrc_reg_state;
>   		u64 lrc_desc;
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 7314e548fb4e..8a49323f6672 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -2739,7 +2739,7 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
>   					    struct intel_context *ce)
>   {
>   	struct drm_i915_gem_object *ctx_obj;
> -	struct i915_vma *vma;
> +	struct i915_vma *ggtt_vma, *ppgtt_vma;
>   	uint32_t context_size;
>   	struct intel_ring *ring;
>   	struct i915_timeline *timeline;
> @@ -2762,9 +2762,17 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
>   		goto error_deref_obj;
>   	}
>   
> -	vma = i915_vma_instance(ctx_obj, &ctx->i915->ggtt.base, NULL);
> -	if (IS_ERR(vma)) {
> -		ret = PTR_ERR(vma);
> +	ggtt_vma = i915_vma_instance(ctx_obj, &ctx->i915->ggtt.base, NULL);
> +	if (IS_ERR(ggtt_vma)) {
> +		ret = PTR_ERR(ggtt_vma);
> +		goto error_deref_obj;
> +	}
> +
> +	ppgtt_vma = i915_vma_instance(ctx_obj,
> +				      &ctx->i915->kernel_context->ppgtt->base,
This is dangerous if someone decides to use 'aliasing ppgtt' 
(enable_ppgtt=1 is still a valid option).

You'll need something like this,
struct i915_hw_ppgtt *ppgtt = ctx->i915->kernel_context->ppgtt ?:
					ctx->i915->mm.aliasing_ppgtt;


> +				      NULL);
> +	if (IS_ERR(ppgtt_vma)) {
> +		ret = PTR_ERR(ppgtt_vma);
>   		goto error_deref_obj;
>   	}
>   
> @@ -2788,7 +2796,8 @@ static int execlists_context_deferred_alloc(struct i915_gem_context *ctx,
>   	}
>   
>   	ce->ring = ring;
> -	ce->state = vma;
> +	ce->state = ggtt_vma;
> +	ce->kernel_state = ppgtt_vma;
>   
>   	return 0;
>   
>