Re: [PATCH 17/18] drm/i915: Use a slab for object allocation

[Paulo Zanoni <przanoni@gmail.com>]

Hi

2012/10/19 Chris Wilson <chris@chris-wilson.co.uk>:
> The primary purpose of this was to debug some use-after-free memory
> corruption that was causing an OOPS inside drm/i915. As it turned out
> the corruption was being caused elsewhere and i915.ko as a major user of
> many objects was being hit hardest.
>
> Indeed as we do frequent the generic kmalloc caches, dedicating one to
> ourselves (or at least naming one for us depending upon the core) aids
> debugging our own slab usage.
>
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Reviewed-by: Jesse Barnes <jbarnes@virtuousgeek.org>

So I applied patches 1-17 in 2 machines (SNB and HSW). Patch 18 does
not apply anymore, it needs to be rebased, so I did not apply it. Both
machines boot and work fine without any unusual errors.

While running "dmesg | grep stolen" one machines tells me it found
32mb and it matches the "pre-allocated" option on my BIOS. The other
machine gives me 64mb but I couldn't find anything related to this on
the BIOS. In both cases the PCI message "detected XXXK stolen memory"
matches the amount print by i915_gem_init_stolen.

On the SNB machine which had 64mb of stolen memory I also see
"reserving 33554432 bytes of contiguous stolen space for FBC".

I'm not sure if this is enough for a tested-by tag, so feel free to
add if you think this test was enough. Please tell me if I need to
test something else.
Tested-by: Paulo Zanoni <paulo.r.zanoni@intel.com>

Thanks,
Paulo

> ---
>  drivers/gpu/drm/i915/i915_dma.c        |    3 +++
>  drivers/gpu/drm/i915/i915_drv.h        |    4 ++++
>  drivers/gpu/drm/i915/i915_gem.c        |   28 +++++++++++++++++++++++-----
>  drivers/gpu/drm/i915/i915_gem_dmabuf.c |    5 ++---
>  drivers/gpu/drm/i915/i915_gem_stolen.c |    4 ++--
>  5 files changed, 34 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
> index 14271aa..69969be 100644
> --- a/drivers/gpu/drm/i915/i915_dma.c
> +++ b/drivers/gpu/drm/i915/i915_dma.c
> @@ -1776,6 +1776,9 @@ int i915_driver_unload(struct drm_device *dev)
>
>         destroy_workqueue(dev_priv->wq);
>
> +       if (dev_priv->slab)
> +               kmem_cache_destroy(dev_priv->slab);
> +
>         pci_dev_put(dev_priv->bridge_dev);
>         kfree(dev->dev_private);
>
> diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
> index 5a0e0cd..5084b29 100644
> --- a/drivers/gpu/drm/i915/i915_drv.h
> +++ b/drivers/gpu/drm/i915/i915_drv.h
> @@ -398,6 +398,7 @@ struct intel_gmbus {
>
>  typedef struct drm_i915_private {
>         struct drm_device *dev;
> +       struct kmem_cache *slab;
>
>         const struct intel_device_info *info;
>
> @@ -1341,12 +1342,15 @@ int i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
>  int i915_gem_wait_ioctl(struct drm_device *dev, void *data,
>                         struct drm_file *file_priv);
>  void i915_gem_load(struct drm_device *dev);
> +void *i915_gem_object_alloc(struct drm_device *dev);
> +void i915_gem_object_free(struct drm_i915_gem_object *obj);
>  int i915_gem_init_object(struct drm_gem_object *obj);
>  void i915_gem_object_init(struct drm_i915_gem_object *obj,
>                          const struct drm_i915_gem_object_ops *ops);
>  struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
>                                                   size_t size);
>  void i915_gem_free_object(struct drm_gem_object *obj);
> +
>  int __must_check i915_gem_object_pin(struct drm_i915_gem_object *obj,
>                                      uint32_t alignment,
>                                      bool map_and_fenceable,
> diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
> index 0349899..8183c0f 100644
> --- a/drivers/gpu/drm/i915/i915_gem.c
> +++ b/drivers/gpu/drm/i915/i915_gem.c
> @@ -193,6 +193,18 @@ i915_gem_get_aperture_ioctl(struct drm_device *dev, void *data,
>         return 0;
>  }
>
> +void *i915_gem_object_alloc(struct drm_device *dev)
> +{
> +       struct drm_i915_private *dev_priv = dev->dev_private;
> +       return kmem_cache_alloc(dev_priv->slab, GFP_KERNEL | __GFP_ZERO);
> +}
> +
> +void i915_gem_object_free(struct drm_i915_gem_object *obj)
> +{
> +       struct drm_i915_private *dev_priv = obj->base.dev->dev_private;
> +       kmem_cache_free(dev_priv->slab, obj);
> +}
> +
>  static int
>  i915_gem_create(struct drm_file *file,
>                 struct drm_device *dev,
> @@ -216,7 +228,7 @@ i915_gem_create(struct drm_file *file,
>         if (ret) {
>                 drm_gem_object_release(&obj->base);
>                 i915_gem_info_remove_obj(dev->dev_private, obj->base.size);
> -               kfree(obj);
> +               i915_gem_object_free(obj);
>                 return ret;
>         }
>
> @@ -3780,12 +3792,12 @@ struct drm_i915_gem_object *i915_gem_alloc_object(struct drm_device *dev,
>         struct address_space *mapping;
>         u32 mask;
>
> -       obj = kzalloc(sizeof(*obj), GFP_KERNEL);
> +       obj = i915_gem_object_alloc(dev);
>         if (obj == NULL)
>                 return NULL;
>
>         if (drm_gem_object_init(dev, &obj->base, size) != 0) {
> -               kfree(obj);
> +               i915_gem_object_free(obj);
>                 return NULL;
>         }
>
> @@ -3868,7 +3880,7 @@ void i915_gem_free_object(struct drm_gem_object *gem_obj)
>         i915_gem_info_remove_obj(dev_priv, obj->base.size);
>
>         kfree(obj->bit_17);
> -       kfree(obj);
> +       i915_gem_object_free(obj);
>  }
>
>  int
> @@ -4246,8 +4258,14 @@ init_ring_lists(struct intel_ring_buffer *ring)
>  void
>  i915_gem_load(struct drm_device *dev)
>  {
> -       int i;
>         drm_i915_private_t *dev_priv = dev->dev_private;
> +       int i;
> +
> +       dev_priv->slab =
> +               kmem_cache_create("i915_gem_object",
> +                                 sizeof(struct drm_i915_gem_object), 0,
> +                                 SLAB_HWCACHE_ALIGN,
> +                                 NULL);
>
>         INIT_LIST_HEAD(&dev_priv->mm.active_list);
>         INIT_LIST_HEAD(&dev_priv->mm.inactive_list);
> diff --git a/drivers/gpu/drm/i915/i915_gem_dmabuf.c b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> index ca3497e..f307e31 100644
> --- a/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> +++ b/drivers/gpu/drm/i915/i915_gem_dmabuf.c
> @@ -276,8 +276,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
>         if (IS_ERR(attach))
>                 return ERR_CAST(attach);
>
> -
> -       obj = kzalloc(sizeof(*obj), GFP_KERNEL);
> +       obj = i915_gem_object_alloc(dev);
>         if (obj == NULL) {
>                 ret = -ENOMEM;
>                 goto fail_detach;
> @@ -285,7 +284,7 @@ struct drm_gem_object *i915_gem_prime_import(struct drm_device *dev,
>
>         ret = drm_gem_private_object_init(dev, &obj->base, dma_buf->size);
>         if (ret) {
> -               kfree(obj);
> +               i915_gem_object_free(obj);
>                 goto fail_detach;
>         }
>
> diff --git a/drivers/gpu/drm/i915/i915_gem_stolen.c b/drivers/gpu/drm/i915/i915_gem_stolen.c
> index 86c4af4..d7cfa71 100644
> --- a/drivers/gpu/drm/i915/i915_gem_stolen.c
> +++ b/drivers/gpu/drm/i915/i915_gem_stolen.c
> @@ -261,7 +261,7 @@ _i915_gem_object_create_stolen(struct drm_device *dev,
>  {
>         struct drm_i915_gem_object *obj;
>
> -       obj = kzalloc(sizeof(*obj), GFP_KERNEL);
> +       obj = i915_gem_object_alloc(dev);
>         if (obj == NULL)
>                 return NULL;
>
> @@ -286,7 +286,7 @@ _i915_gem_object_create_stolen(struct drm_device *dev,
>         return obj;
>
>  cleanup:
> -       kfree(obj);
> +       i915_gem_object_free(obj);
>         return NULL;
>  }
>
> --
> 1.7.10.4
>
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-- 
Paulo Zanoni