Re: [PATCH v4 14/17] drm/i915/pxp: User interface for Protected buffer

[Daniel Vetter <daniel@ffwll.ch>]

On Mon, May 24, 2021 at 10:48:00PM -0700, Daniele Ceraolo Spurio wrote:
> From: Bommu Krishnaiah <krishnaiah.bommu@intel.com>
> 
> This api allow user mode to create Protected buffers. Only contexts
> marked as protected are allowed to operate on protected buffers.
> 
> We only allow setting the flags at creation time.
> 
> All protected objects that have backing storage will be considered
> invalid when the session is destroyed and they won't be usable anymore.
> 
> Given that the PXP HW supports multiple modes (but we currently only
> care about one), a flag variable has been reserved in the structure
> used in the create_ext ioctl for possible future updates.
> 
> This is a rework of the original code by Bommu Krishnaiah. I've kept
> authorship unchanged since significant chunks have not been modified.
> 
> v2: split context changes, fix defines and improve documentation (Chris),
>     add object invalidation logic
> v3: fix spinlock definition and usage, only validate objects when
>     they're first added to a context lut, only remove them once (Chris),
>     make protected context flag not mandatory in protected object execbuf
>     to avoid abuse (Lionel)
> v4: rebase to new gem_create_ext
> 
> Signed-off-by: Bommu Krishnaiah <krishnaiah.bommu@intel.com>
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio@intel.com>
> Cc: Telukuntla Sreedhar <sreedhar.telukuntla@intel.com>
> Cc: Kondapally Kalyan <kalyan.kondapally@intel.com>
> Cc: Gupta Anshuman <Anshuman.Gupta@intel.com>
> Cc: Huang Sean Z <sean.z.huang@intel.com>
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
> Cc: Jason Ekstrand <jason@jlekstrand.net>
> Cc: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/i915/gem/i915_gem_create.c    | 26 ++++++++++++
>  .../gpu/drm/i915/gem/i915_gem_execbuffer.c    | 15 +++++++
>  drivers/gpu/drm/i915/gem/i915_gem_object.c    |  6 +++
>  drivers/gpu/drm/i915/gem/i915_gem_object.h    | 12 ++++++
>  .../gpu/drm/i915/gem/i915_gem_object_types.h  | 13 ++++++
>  drivers/gpu/drm/i915/pxp/intel_pxp.c          | 41 +++++++++++++++++++
>  drivers/gpu/drm/i915/pxp/intel_pxp.h          | 13 ++++++
>  drivers/gpu/drm/i915/pxp/intel_pxp_types.h    |  5 +++
>  include/uapi/drm/i915_drm.h                   | 33 ++++++++++++++-
>  9 files changed, 163 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_create.c b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> index 548ddf39d853..c14be3882c35 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_create.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_create.c
> @@ -6,6 +6,7 @@
>  #include "gem/i915_gem_ioctls.h"
>  #include "gem/i915_gem_lmem.h"
>  #include "gem/i915_gem_region.h"
> +#include "pxp/intel_pxp.h"
>  
>  #include "i915_drv.h"
>  #include "i915_trace.h"
> @@ -99,7 +100,11 @@ i915_gem_setup(struct drm_i915_gem_object *obj, u64 size)
>  
>  	GEM_BUG_ON(size != obj->base.size);
>  
> +	if (obj->user_flags & I915_GEM_OBJECT_PROTECTED)
> +		intel_pxp_object_add(obj);
> +
>  	trace_i915_gem_object_create(obj);
> +
>  	return 0;
>  }
>  
> @@ -344,8 +349,29 @@ static int ext_set_placements(struct i915_user_extension __user *base,
>  	return set_placements(&ext, data);
>  }
>  
> +static int ext_set_protected(struct i915_user_extension __user *base, void *data)
> +{
> +	struct drm_i915_gem_create_ext_protected_content ext;
> +	struct create_ext *ext_data = data;
> +
> +	if (copy_from_user(&ext, base, sizeof(ext)))
> +		return -EFAULT;
> +
> +	if (ext.flags)
> +		return -EINVAL;
> +
> +	if (!intel_pxp_is_enabled(&ext_data->i915->gt.pxp))
> +		return -ENODEV;
> +
> +	ext_data->vanilla_object->user_flags |= I915_GEM_OBJECT_PROTECTED;
> +
> +	return 0;
> +}
> +
> +
>  static const i915_user_extension_fn create_extensions[] = {
>  	[I915_GEM_CREATE_EXT_MEMORY_REGIONS] = ext_set_placements,
> +	[I915_GEM_CREATE_EXT_PROTECTED_CONTENT] = ext_set_protected,
>  };
>  
>  /**
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> index c08e28847064..5dd813d04a9f 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_execbuffer.c
> @@ -839,6 +839,21 @@ static struct i915_vma *eb_lookup_vma(struct i915_execbuffer *eb, u32 handle)
>  		if (unlikely(!obj))
>  			return ERR_PTR(-ENOENT);
>  
> +		/*
> +		 * If the user has opted-in for protected-object tracking, make
> +		 * sure the object encryption can be used.
> +		 * We only need to do this when the object is first used with
> +		 * this context, because the context itself will be banned when
> +		 * the protected objects become invalid.
> +		 */
> +		if (i915_gem_context_uses_protected_content(eb->gem_context) &&
> +		    i915_gem_object_is_protected(obj)) {
> +			if (!intel_pxp_is_active(&vm->gt->pxp))
> +				return ERR_PTR(-ENODEV);
> +			if (!i915_gem_object_has_valid_protection(obj))
> +				return ERR_PTR(-ENOEXEC);
> +		}
> +
>  		vma = i915_vma_instance(obj, vm, NULL);
>  		if (IS_ERR(vma)) {
>  			i915_gem_object_put(obj);
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.c b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> index 28144410df86..b47fa0a7b25a 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.c
> @@ -25,6 +25,7 @@
>  #include <linux/sched/mm.h>
>  
>  #include "display/intel_frontbuffer.h"
> +#include "pxp/intel_pxp.h"
>  #include "i915_drv.h"
>  #include "i915_gem_clflush.h"
>  #include "i915_gem_context.h"
> @@ -70,6 +71,8 @@ void i915_gem_object_init(struct drm_i915_gem_object *obj,
>  	INIT_LIST_HEAD(&obj->lut_list);
>  	spin_lock_init(&obj->lut_lock);
>  
> +	INIT_LIST_HEAD(&obj->pxp_link);
> +
>  	spin_lock_init(&obj->mmo.lock);
>  	obj->mmo.offsets = RB_ROOT;
>  
> @@ -232,6 +235,9 @@ static void __i915_gem_free_objects(struct drm_i915_private *i915,
>  			spin_unlock(&obj->vma.lock);
>  		}
>  
> +		if (i915_gem_object_has_valid_protection(obj))
> +			intel_pxp_object_remove(obj);
> +
>  		__i915_gem_object_free_mmaps(obj);
>  
>  		GEM_BUG_ON(!list_empty(&obj->lut_list));
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object.h b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> index 2ebd79537aea..61b101560352 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object.h
> @@ -288,6 +288,18 @@ i915_gem_object_never_mmap(const struct drm_i915_gem_object *obj)
>  	return i915_gem_object_type_has(obj, I915_GEM_OBJECT_NO_MMAP);
>  }
>  
> +static inline bool
> +i915_gem_object_is_protected(const struct drm_i915_gem_object *obj)
> +{
> +	return obj->user_flags & I915_GEM_OBJECT_PROTECTED;
> +}
> +
> +static inline bool
> +i915_gem_object_has_valid_protection(const struct drm_i915_gem_object *obj)
> +{
> +	return i915_gem_object_is_protected(obj) && !list_empty(&obj->pxp_link);
> +}
> +
>  static inline bool
>  i915_gem_object_is_framebuffer(const struct drm_i915_gem_object *obj)
>  {
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> index 0727d0c76aa0..a698ad0ef7f6 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -167,6 +167,11 @@ struct drm_i915_gem_object {
>  	} mmo;
>  
>  	I915_SELFTEST_DECLARE(struct list_head st_link);
> +	/**
> +	 * @user_flags: small set of booleans set by the user
> +	 */
> +	unsigned long user_flags;
> +#define I915_GEM_OBJECT_PROTECTED BIT(0)
>  
>  	unsigned long flags;
>  #define I915_BO_ALLOC_CONTIGUOUS BIT(0)
> @@ -294,6 +299,14 @@ struct drm_i915_gem_object {
>  		bool dirty:1;
>  	} mm;
>  
> +	/*
> +	 * When the PXP session is invalidated, we need to mark all protected
> +	 * objects as invalid. To easily do so we add them all to a list. The
> +	 * presence on the list is used to check if the encryption is valid or
> +	 * not.
> +	 */
> +	struct list_head pxp_link;
> +
>  	/** Record of address bit 17 of each page at last unbind. */
>  	unsigned long *bit_17;
>  
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.c b/drivers/gpu/drm/i915/pxp/intel_pxp.c
> index 2291c68fd3a0..e6a59eb05eae 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp.c
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp.c
> @@ -69,6 +69,9 @@ void intel_pxp_init(struct intel_pxp *pxp)
>  	if (!HAS_PXP(gt->i915))
>  		return;
>  
> +	spin_lock_init(&pxp->lock);
> +	INIT_LIST_HEAD(&pxp->protected_objects);
> +
>  	/*
>  	 * we'll use the completion to check if there is a termination pending,
>  	 * so we start it as completed and we reinit it when a termination
> @@ -177,11 +180,49 @@ void intel_pxp_fini_hw(struct intel_pxp *pxp)
>  	intel_pxp_irq_disable(pxp);
>  }
>  
> +int intel_pxp_object_add(struct drm_i915_gem_object *obj)
> +{
> +	struct intel_pxp *pxp = &to_i915(obj->base.dev)->gt.pxp;
> +
> +	if (!intel_pxp_is_enabled(pxp))
> +		return -ENODEV;
> +
> +	if (!list_empty(&obj->pxp_link))
> +		return -EEXIST;
> +
> +	spin_lock_irq(&pxp->lock);
> +	list_add(&obj->pxp_link, &pxp->protected_objects);
> +	spin_unlock_irq(&pxp->lock);
> +
> +	return 0;
> +}
> +
> +void intel_pxp_object_remove(struct drm_i915_gem_object *obj)
> +{
> +	struct intel_pxp *pxp = &to_i915(obj->base.dev)->gt.pxp;
> +
> +	if (!intel_pxp_is_enabled(pxp))
> +		return;
> +
> +	spin_lock_irq(&pxp->lock);
> +	list_del_init(&obj->pxp_link);
> +	spin_unlock_irq(&pxp->lock);
> +}
> +
>  void intel_pxp_invalidate(struct intel_pxp *pxp)
>  {
>  	struct drm_i915_private *i915 = pxp_to_gt(pxp)->i915;
> +	struct drm_i915_gem_object *obj, *tmp;
>  	struct i915_gem_context *ctx, *cn;
>  
> +	/* delete objects that have been used with the invalidated session */
> +	spin_lock_irq(&pxp->lock);
> +	list_for_each_entry_safe(obj, tmp, &pxp->protected_objects, pxp_link) {
> +		if (i915_gem_object_has_pages(obj))
> +			list_del_init(&obj->pxp_link);
> +	}
> +	spin_unlock_irq(&pxp->lock);
> +
>  	/* ban all contexts marked as protected */
>  	spin_lock_irq(&i915->gem.contexts.lock);
>  	list_for_each_entry_safe(ctx, cn, &i915->gem.contexts.list, link) {
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp.h b/drivers/gpu/drm/i915/pxp/intel_pxp.h
> index 1f9871e64096..3500d7896058 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp.h
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp.h
> @@ -9,6 +9,8 @@
>  #include "gt/intel_gt_types.h"
>  #include "intel_pxp_types.h"
>  
> +struct drm_i915_gem_object;
> +
>  static inline struct intel_gt *pxp_to_gt(const struct intel_pxp *pxp)
>  {
>  	return container_of(pxp, struct intel_gt, pxp);
> @@ -33,6 +35,9 @@ void intel_pxp_fini_hw(struct intel_pxp *pxp);
>  
>  void intel_pxp_mark_termination_in_progress(struct intel_pxp *pxp);
>  int intel_pxp_start(struct intel_pxp *pxp);
> +
> +int intel_pxp_object_add(struct drm_i915_gem_object *obj);
> +void intel_pxp_object_remove(struct drm_i915_gem_object *obj);
>  void intel_pxp_invalidate(struct intel_pxp *pxp);
>  #else
>  static inline void intel_pxp_init(struct intel_pxp *pxp)
> @@ -47,6 +52,14 @@ static inline int intel_pxp_start(struct intel_pxp *pxp)
>  {
>  	return 0;
>  }
> +
> +static inline int intel_pxp_object_add(struct drm_i915_gem_object *obj)
> +{
> +	return 0;
> +}
> +static inline void intel_pxp_object_remove(struct drm_i915_gem_object *obj)
> +{
> +}
>  #endif
>  
>  #endif /* __INTEL_PXP_H__ */
> diff --git a/drivers/gpu/drm/i915/pxp/intel_pxp_types.h b/drivers/gpu/drm/i915/pxp/intel_pxp_types.h
> index b3ae49dd73a8..cc510416eac6 100644
> --- a/drivers/gpu/drm/i915/pxp/intel_pxp_types.h
> +++ b/drivers/gpu/drm/i915/pxp/intel_pxp_types.h
> @@ -7,7 +7,9 @@
>  #define __INTEL_PXP_TYPES_H__
>  
>  #include <linux/completion.h>
> +#include <linux/list.h>
>  #include <linux/mutex.h>
> +#include <linux/spinlock.h>
>  #include <linux/types.h>
>  #include <linux/workqueue.h>
>  
> @@ -43,6 +45,9 @@ struct intel_pxp {
>  #define PXP_TERMINATION_REQUEST  BIT(0)
>  #define PXP_TERMINATION_COMPLETE BIT(1)
>  #define PXP_INVAL_REQUIRED       BIT(2)
> +
> +	spinlock_t lock; /* protects the objects list */
> +	struct list_head protected_objects;
>  };
>  
>  #endif /* __INTEL_PXP_TYPES_H__ */
> diff --git a/include/uapi/drm/i915_drm.h b/include/uapi/drm/i915_drm.h
> index 3cc33fcbf520..d39b8cb4bfc5 100644
> --- a/include/uapi/drm/i915_drm.h
> +++ b/include/uapi/drm/i915_drm.h

For easier review it would be nice to have all the uapi and its kerneldoc
in one patch. I feel like I've missed parts.

> @@ -1768,7 +1768,7 @@ struct drm_i915_gem_context_param {
>  	__u64 value;
>  };
>  
> -/*
> +/**
>   * Context SSEU programming
>   *
>   * It may be necessary for either functional or performance reason to configure
> @@ -2669,8 +2669,12 @@ struct drm_i915_gem_create_ext {
>  	 *
>  	 * For I915_GEM_CREATE_EXT_MEMORY_REGIONS usage see
>  	 * struct drm_i915_gem_create_ext_memory_regions.
> +	 *
> +	 * For I915_GEM_CREATE_EXT_PROTECTED_CONTENT usage see
> +	 * struct drm_i915_gem_create_ext_protected_content.
>  	 */
>  #define I915_GEM_CREATE_EXT_MEMORY_REGIONS 0
> +#define I915_GEM_CREATE_EXT_PROTECTED_CONTENT 1
>  	__u64 extensions;
>  };
>  
> @@ -2728,6 +2732,33 @@ struct drm_i915_gem_create_ext_memory_regions {
>  	__u64 regions;
>  };
>  
> +/**
> + * struct drm_i915_gem_create_ext_protected_content - The
> + * I915_OBJECT_PARAM_PROTECTED_CONTENT extension.
> + *
> + * If this extension is provided, buffer contents are expected to be
> + * protected by PXP encryption and requires decryption for scan out
> + * and processing. This is only possible on platforms that have PXP enabled,
> + * on all other scenarios ysing this extension will cause the ioctl to fail
> + * and return -ENODEV. The flags parameter is reserved for future expansion and
> + * must currently be set to zero.
> + *
> + * The buffer contents are considered invalid after a PXP session teardown.
> + *
> + * The encryption is guaranteed to be processed correctly only if the object
> + * is submitted with a context created using the
> + * I915_CONTEXT_PARAM_PROTECTED_CONTENT flag. This will also enable extra checks

Not finding the kerneldoc for this. Also is this a CTX_CREATE_EXT flag, so
guaranteed to be immutable, or is this another CTX_SETPARAM flag, which
would be mutable and we really want to get away from that paradigm?

> + * at submission time on the validity of the objects involved, which can lead to
> + * the following errors being returned from the execbuf ioctl:

I think this also should be put into the execbuf ioctl structs. Plus I
think RESET_STATS should also explain how this interacts and all that.
Here we should just reference this other sections imo.

Yes this means a bit more to type because not even the bare bones of these
other ioctl kerneldocs exists, but we have to start somewhere.

Cheers, Daniel

> + *
> + * -ENODEV: PXP session not currently active
> + * -ENOEXEC: buffer has become invalid after a teardown event
> + */
> +struct drm_i915_gem_create_ext_protected_content {
> +	struct i915_user_extension base;
> +	__u32 flags;
> +};
> +
>  /* ID of the protected content session managed by i915 when PXP is active */
>  #define I915_PROTECTED_CONTENT_DEFAULT_SESSION 0xf
>  
> -- 
> 2.29.2
> 

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