Re: [PATCH 16/18] drm/i915/gtt: One instance of scratch page table/directory

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On Thu, Jun 25, 2015 at 06:35:18PM +0300, Mika Kuoppala wrote:
> +static int setup_scratch(struct i915_address_space *vm)
> +{
> +	struct i915_address_space *ggtt_vm = &to_i915(vm->dev)->gtt.base;
> +
> +	if (i915_is_ggtt(vm))
> +		return setup_scratch_ggtt(vm);
> +
> +	vm->scratch_page = ggtt_vm->scratch_page;
> +	vm->scratch_pt = ggtt_vm->scratch_pt;
> +	vm->scratch_pd = ggtt_vm->scratch_pd;
> +
> +	return 0;
> +}

The point of a ppgtt is full isolation, sharing the scratch page destroys
that. Hence nack. If you want a bit of polish, renaming initialize_pd/pt
to initialize_scratch_pd/pt would make sense though I think.
-Daniel

> +
> +static void check_scratch_page(struct i915_address_space *vm)
> +{
> +	struct i915_hw_ppgtt *ppgtt =
> +		container_of(vm, struct i915_hw_ppgtt, base);
> +	int i;
> +	u64 *vaddr;
> +
> +	vaddr = kmap_px(vm->scratch_page);
> +
> +	for (i = 0; i < PAGE_SIZE / sizeof(u64); i++) {
> +		if (vaddr[i] == SCRATCH_PAGE_MAGIC)
> +			continue;
> +
> +		DRM_ERROR("%p scratch[%d] = 0x%08llx\n", vm, i, vaddr[i]);
> +		break;
> +	}
> +
> +	kunmap_px(ppgtt, vaddr);
> +}
> +
> +static void cleanup_scratch_ggtt(struct i915_address_space *vm)
> +{
> +	check_scratch_page(vm);
> +	free_scratch_page(vm);
> +
> +	if (INTEL_INFO(vm->dev)->gen < 6)
> +		return;
> +
> +	free_pt(vm->dev, vm->scratch_pt);
> +
> +	if (INTEL_INFO(vm->dev)->gen >= 8)
> +		free_pd(vm->dev, vm->scratch_pd);
> +}
> +
> +static void cleanup_scratch(struct i915_address_space *vm)
> +{
> +	if (i915_is_ggtt(vm))
> +		cleanup_scratch_ggtt(vm);
> +
> +	vm->scratch_page = NULL;
> +	vm->scratch_pt = NULL;
> +	vm->scratch_pd = NULL;
> +}
> +
>  /* Broadwell Page Directory Pointer Descriptors */
>  static int gen8_write_pdp(struct drm_i915_gem_request *req,
>  			  unsigned entry,
> @@ -525,7 +686,7 @@ static void gen8_ppgtt_clear_range(struct i915_address_space *vm,
>  	unsigned num_entries = length >> PAGE_SHIFT;
>  	unsigned last_pte, i;
>  
> -	scratch_pte = gen8_pte_encode(px_dma(ppgtt->base.scratch_page),
> +	scratch_pte = gen8_pte_encode(px_dma(vm->scratch_page),
>  				      I915_CACHE_LLC, use_scratch);
>  
>  	while (num_entries) {
> @@ -609,16 +770,6 @@ static void gen8_ppgtt_insert_entries(struct i915_address_space *vm,
>  		kunmap_px(ppgtt, pt_vaddr);
>  }
>  
> -static void gen8_initialize_pd(struct i915_address_space *vm,
> -			       struct i915_page_directory *pd)
> -{
> -	gen8_pde_t scratch_pde;
> -
> -	scratch_pde = gen8_pde_encode(px_dma(vm->scratch_pt), I915_CACHE_LLC);
> -
> -	fill_px(vm->dev, pd, scratch_pde);
> -}
> -
>  static void gen8_free_page_tables(struct i915_page_directory *pd, struct drm_device *dev)
>  {
>  	int i;
> @@ -649,8 +800,7 @@ static void gen8_ppgtt_cleanup(struct i915_address_space *vm)
>  		free_pd(ppgtt->base.dev, ppgtt->pdp.page_directory[i]);
>  	}
>  
> -	free_pd(vm->dev, vm->scratch_pd);
> -	free_pt(vm->dev, vm->scratch_pt);
> +	cleanup_scratch(vm);
>  }
>  
>  /**
> @@ -937,16 +1087,7 @@ err_out:
>   */
>  static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>  {
> -	ppgtt->base.scratch_pt = alloc_pt(ppgtt->base.dev);
> -	if (IS_ERR(ppgtt->base.scratch_pt))
> -		return PTR_ERR(ppgtt->base.scratch_pt);
> -
> -	ppgtt->base.scratch_pd = alloc_pd(ppgtt->base.dev);
> -	if (IS_ERR(ppgtt->base.scratch_pd))
> -		return PTR_ERR(ppgtt->base.scratch_pd);
> -
> -	gen8_initialize_pt(&ppgtt->base, ppgtt->base.scratch_pt);
> -	gen8_initialize_pd(&ppgtt->base, ppgtt->base.scratch_pd);
> +	int ret;
>  
>  	ppgtt->base.start = 0;
>  	ppgtt->base.total = 1ULL << 32;
> @@ -966,6 +1107,10 @@ static int gen8_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>  
>  	ppgtt->switch_mm = gen8_mm_switch;
>  
> +	ret = setup_scratch(&ppgtt->base);
> +	if (ret)
> +		return ret;
> +
>  	return 0;
>  }
>  
> @@ -1272,19 +1417,6 @@ static void gen6_ppgtt_insert_entries(struct i915_address_space *vm,
>  		kunmap_px(ppgtt, pt_vaddr);
>  }
>  
> -static void gen6_initialize_pt(struct i915_address_space *vm,
> -			       struct i915_page_table *pt)
> -{
> -	gen6_pte_t scratch_pte;
> -
> -	WARN_ON(px_dma(vm->scratch_page) == 0);
> -
> -	scratch_pte = vm->pte_encode(px_dma(vm->scratch_page),
> -				     I915_CACHE_LLC, true, 0);
> -
> -	fill32_px(vm->dev, pt, scratch_pte);
> -}
> -
>  static int gen6_alloc_va_range(struct i915_address_space *vm,
>  			       uint64_t start_in, uint64_t length_in)
>  {
> @@ -1389,7 +1521,7 @@ static void gen6_ppgtt_cleanup(struct i915_address_space *vm)
>  			free_pt(ppgtt->base.dev, pt);
>  	}
>  
> -	free_pt(vm->dev, vm->scratch_pt);
> +	cleanup_scratch(vm);
>  }
>  
>  static int gen6_ppgtt_allocate_page_directories(struct i915_hw_ppgtt *ppgtt)
> @@ -1404,11 +1536,10 @@ static int gen6_ppgtt_allocate_page_directories(struct i915_hw_ppgtt *ppgtt)
>  	 * size. We allocate at the top of the GTT to avoid fragmentation.
>  	 */
>  	BUG_ON(!drm_mm_initialized(&dev_priv->gtt.base.mm));
> -	ppgtt->base.scratch_pt = alloc_pt(ppgtt->base.dev);
> -	if (IS_ERR(ppgtt->base.scratch_pt))
> -		return PTR_ERR(ppgtt->base.scratch_pt);
>  
> -	gen6_initialize_pt(&ppgtt->base, ppgtt->base.scratch_pt);
> +	ret = setup_scratch(&ppgtt->base);
> +	if (ret)
> +		return ret;
>  
>  alloc:
>  	ret = drm_mm_insert_node_in_range_generic(&dev_priv->gtt.base.mm,
> @@ -1439,7 +1570,7 @@ alloc:
>  	return 0;
>  
>  err_out:
> -	free_pt(ppgtt->base.dev, ppgtt->base.scratch_pt);
> +	cleanup_scratch(&ppgtt->base);
>  	return ret;
>  }
>  
> @@ -1513,10 +1644,7 @@ static int gen6_ppgtt_init(struct i915_hw_ppgtt *ppgtt)
>  
>  static int __hw_ppgtt_init(struct drm_device *dev, struct i915_hw_ppgtt *ppgtt)
>  {
> -	struct drm_i915_private *dev_priv = dev->dev_private;
> -
>  	ppgtt->base.dev = dev;
> -	ppgtt->base.scratch_page = dev_priv->gtt.base.scratch_page;
>  
>  	if (INTEL_INFO(dev)->gen < 8)
>  		return gen6_ppgtt_init(ppgtt);
> @@ -2124,45 +2252,6 @@ void i915_global_gtt_cleanup(struct drm_device *dev)
>  	vm->cleanup(vm);
>  }
>  
> -#define SCRATCH_PAGE_MAGIC 0xffff00ffffff00ffULL
> -
> -static int alloc_scratch_page(struct i915_address_space *vm)
> -{
> -	struct i915_page_scratch *sp;
> -	int ret;
> -
> -	WARN_ON(vm->scratch_page);
> -
> -	sp = kzalloc(sizeof(*sp), GFP_KERNEL);
> -	if (sp == NULL)
> -		return -ENOMEM;
> -
> -	ret = __setup_page_dma(vm->dev, px_base(sp), GFP_DMA32 | __GFP_ZERO);
> -	if (ret) {
> -		kfree(sp);
> -		return ret;
> -	}
> -
> -	fill_px(vm->dev, sp, SCRATCH_PAGE_MAGIC);
> -	set_pages_uc(px_page(sp), 1);
> -
> -	vm->scratch_page = sp;
> -
> -	return 0;
> -}
> -
> -static void free_scratch_page(struct i915_address_space *vm)
> -{
> -	struct i915_page_scratch *sp = vm->scratch_page;
> -
> -	set_pages_wb(px_page(sp), 1);
> -
> -	cleanup_px(vm->dev, sp);
> -	kfree(sp);
> -
> -	vm->scratch_page = NULL;
> -}
> -
>  static unsigned int gen6_get_total_gtt_size(u16 snb_gmch_ctl)
>  {
>  	snb_gmch_ctl >>= SNB_GMCH_GGMS_SHIFT;
> @@ -2246,7 +2335,6 @@ static int ggtt_probe_common(struct drm_device *dev,
>  {
>  	struct drm_i915_private *dev_priv = dev->dev_private;
>  	phys_addr_t gtt_phys_addr;
> -	int ret;
>  
>  	/* For Modern GENs the PTEs and register space are split in the BAR */
>  	gtt_phys_addr = pci_resource_start(dev->pdev, 0) +
> @@ -2268,14 +2356,7 @@ static int ggtt_probe_common(struct drm_device *dev,
>  		return -ENOMEM;
>  	}
>  
> -	ret = alloc_scratch_page(&dev_priv->gtt.base);
> -	if (ret) {
> -		DRM_ERROR("Scratch setup failed\n");
> -		/* iounmap will also get called at remove, but meh */
> -		iounmap(dev_priv->gtt.gsm);
> -	}
> -
> -	return ret;
> +	return setup_scratch(&dev_priv->gtt.base);
>  }
>  
>  /* The GGTT and PPGTT need a private PPAT setup in order to handle cacheability
> @@ -2447,7 +2528,7 @@ static void gen6_gmch_remove(struct i915_address_space *vm)
>  	struct i915_gtt *gtt = container_of(vm, struct i915_gtt, base);
>  
>  	iounmap(gtt->gsm);
> -	free_scratch_page(vm);
> +	cleanup_scratch(vm);
>  }
>  
>  static int i915_gmch_probe(struct drm_device *dev,
> -- 
> 1.9.1
> 
> _______________________________________________
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> Intel-gfx@xxxxxxxxxxxxxxxxxxxxx
> http://lists.freedesktop.org/mailman/listinfo/intel-gfx

-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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