Re: [PATCH v2 14/15] drm/i915: Use ttm mmap handling for ttm bo's.

[Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>]

On 5/18/21 10:27 AM, Thomas Hellström wrote:
> From: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>
>
> Use the ttm handlers for servicing page faults, and vm_access.
>
> Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxxxx>

LGTM. Just need to make sure we don't forget about the caching.

Reviewed-by: Thomas Hellström <thomas.hellstrom@xxxxxxxxxxxxxxx>



> ---
>   drivers/gpu/drm/i915/gem/i915_gem_mman.c      |  17 ++-
>   drivers/gpu/drm/i915/gem/i915_gem_mman.h      |   2 +
>   .../gpu/drm/i915/gem/i915_gem_object_types.h  |   1 +
>   drivers/gpu/drm/i915/gem/i915_gem_ttm.c       | 105 +++++++++++++++++-
>   4 files changed, 118 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.c b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> index 65db290efd16..2bf89349dde9 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.c
> @@ -19,6 +19,7 @@
>   #include "i915_gem_mman.h"
>   #include "i915_trace.h"
>   #include "i915_user_extensions.h"
> +#include "i915_gem_ttm.h"
>   #include "i915_vma.h"
>   
>   static inline bool
> @@ -789,7 +790,7 @@ i915_gem_mmap_offset_ioctl(struct drm_device *dev, void *data,
>   	return __assign_mmap_offset(file, args->handle, type, &args->offset);
>   }
>   
> -static void vm_open(struct vm_area_struct *vma)
> +void i915_gem_mmap_vm_open(struct vm_area_struct *vma)
>   {
>   	struct i915_mmap_offset *mmo = vma->vm_private_data;
>   	struct drm_i915_gem_object *obj = mmo->obj;
> @@ -798,7 +799,7 @@ static void vm_open(struct vm_area_struct *vma)
>   	i915_gem_object_get(obj);
>   }
>   
> -static void vm_close(struct vm_area_struct *vma)
> +void i915_gem_mmap_vm_close(struct vm_area_struct *vma)
>   {
>   	struct i915_mmap_offset *mmo = vma->vm_private_data;
>   	struct drm_i915_gem_object *obj = mmo->obj;
> @@ -810,15 +811,15 @@ static void vm_close(struct vm_area_struct *vma)
>   static const struct vm_operations_struct vm_ops_gtt = {
>   	.fault = vm_fault_gtt,
>   	.access = vm_access,
> -	.open = vm_open,
> -	.close = vm_close,
> +	.open = i915_gem_mmap_vm_open,
> +	.close = i915_gem_mmap_vm_close,
>   };
>   
>   static const struct vm_operations_struct vm_ops_cpu = {
>   	.fault = vm_fault_cpu,
>   	.access = vm_access,
> -	.open = vm_open,
> -	.close = vm_close,
> +	.open = i915_gem_mmap_vm_open,
> +	.close = i915_gem_mmap_vm_close,
>   };
>   
>   static int singleton_release(struct inode *inode, struct file *file)
> @@ -953,6 +954,10 @@ int i915_gem_mmap(struct file *filp, struct vm_area_struct *vma)
>   	}
>   	vma->vm_page_prot = pgprot_decrypted(vma->vm_page_prot);
>   
> +	/* override ops per-object if desired */
> +	if (obj->ops->mmap_ops)
> +		vma->vm_ops = obj->ops->mmap_ops;
> +
>   	return 0;
>   }
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_mman.h b/drivers/gpu/drm/i915/gem/i915_gem_mman.h
> index efee9e0d2508..e5bd02a6db12 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_mman.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_mman.h
> @@ -28,5 +28,7 @@ void __i915_gem_object_release_mmap_gtt(struct drm_i915_gem_object *obj);
>   void i915_gem_object_release_mmap_gtt(struct drm_i915_gem_object *obj);
>   
>   void i915_gem_object_release_mmap_offset(struct drm_i915_gem_object *obj);
> +void i915_gem_mmap_vm_open(struct vm_area_struct *vma);
> +void i915_gem_mmap_vm_close(struct vm_area_struct *vma);
>   
>   #endif
> 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 b350765e1935..31d828e91cf4 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_object_types.h
> @@ -79,6 +79,7 @@ struct drm_i915_gem_object_ops {
>   	void (*delayed_free)(struct drm_i915_gem_object *obj);
>   	void (*release)(struct drm_i915_gem_object *obj);
>   
> +	const struct vm_operations_struct *mmap_ops;
>   	const char *name; /* friendly name for debug, e.g. lockdep classes */
>   };
>   
> diff --git a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> index 790f5ec45c4d..fe9ac50b2470 100644
> --- a/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> +++ b/drivers/gpu/drm/i915/gem/i915_gem_ttm.c
> @@ -14,6 +14,7 @@
>   #include "gem/i915_gem_region.h"
>   #include "gem/i915_gem_ttm.h"
>   #include "gem/i915_gem_ttm_bo_util.h"
> +#include "gem/i915_gem_mman.h"
>   
>   #define I915_PL_LMEM0 TTM_PL_PRIV
>   #define I915_PL_SYSTEM TTM_PL_SYSTEM
> @@ -345,6 +346,44 @@ static int i915_ttm_move(struct ttm_buffer_object *bo, bool evict,
>   	return 0;
>   }
>   
> +static int i915_ttm_io_mem_reserve(struct ttm_device *bdev, struct ttm_resource *mem)
> +{
> +	if (mem->mem_type < I915_PL_LMEM0)
> +		return 0;
> +
> +	/* We may need to revisit this later, but this allows all caching to be used in mmap */
> +	mem->bus.caching = ttm_cached;
> +	mem->bus.is_iomem = true;
> +
> +	return 0;
> +}
> +
> +static unsigned long i915_ttm_io_mem_pfn(struct ttm_buffer_object *bo,
> +					 unsigned long page_offset)
> +{
> +	struct drm_i915_gem_object *obj = i915_ttm_to_gem(bo);
> +	struct sg_table *sgt = obj->ttm.cached_io_st;
> +	struct scatterlist *sg;
> +	unsigned int i;
> +
> +	GEM_WARN_ON(bo->ttm);
> +
> +	for_each_sgtable_dma_sg(sgt, sg, i) {
> +		unsigned long sg_max = sg->length >> PAGE_SHIFT;
> +
> +		if (page_offset < sg_max) {
> +			unsigned long base =
> +				obj->mm.region->iomap.base - obj->mm.region->region.start;
> +
> +			return ((base + sg_dma_address(sg)) >> PAGE_SHIFT) + page_offset;
> +		}
> +
> +		page_offset -= sg_max;
> +	}
> +	GEM_BUG_ON(1);
> +	return 0;
> +}
> +
>   struct ttm_device_funcs i915_ttm_bo_driver = {
>   	.ttm_tt_create = i915_ttm_tt_create,
>   	.ttm_tt_unpopulate = i915_ttm_tt_unpopulate,
> @@ -355,6 +394,8 @@ struct ttm_device_funcs i915_ttm_bo_driver = {
>   	.verify_access = NULL,
>   	.swap_notify = i915_ttm_swap_notify,
>   	.delete_mem_notify = i915_ttm_delete_mem_notify,
> +	.io_mem_reserve = i915_ttm_io_mem_reserve,
> +	.io_mem_pfn = i915_ttm_io_mem_pfn,
>   };
>   
>   static int i915_ttm_get_pages(struct drm_i915_gem_object *obj)
> @@ -454,7 +495,68 @@ static void i915_ttm_delayed_free(struct drm_i915_gem_object *obj)
>   	ttm_bo_put(i915_gem_to_ttm(obj));
>   }
>   
> -static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
> +static vm_fault_t vm_fault_ttm(struct vm_fault *vmf)
> +{
> +	struct vm_area_struct *area = vmf->vma;
> +	struct i915_mmap_offset *mmo = area->vm_private_data;
> +	struct drm_i915_gem_object *obj = mmo->obj;
> +	vm_fault_t ret;
> +
> +	/* Sanity check that we allow writing into this object */
> +	if (unlikely(i915_gem_object_is_readonly(obj) &&
> +		     area->vm_flags & VM_WRITE))
> +		return VM_FAULT_SIGBUS;
> +
> +	ret = ttm_bo_vm_reserve(i915_gem_to_ttm(obj), vmf);
> +	if (ret)
> +		return ret;
> +
> +	ret = ttm_bo_vm_fault_reserved(i915_gem_to_ttm(obj), vmf,
> +				       drm_vma_node_start(&mmo->vma_node),
> +				       vmf->vma->vm_page_prot,
> +				       TTM_BO_VM_NUM_PREFAULT, 1);
> +	if (ret == VM_FAULT_RETRY && !(vmf->flags & FAULT_FLAG_RETRY_NOWAIT))
> +		return ret;
> +
> +	dma_resv_unlock(obj->base.resv);
> +
> +	return ret;
> +}
> +
> +static int
> +vm_access_ttm(struct vm_area_struct *area, unsigned long addr,
> +	  void *buf, int len, int write)
> +{
> +	struct i915_mmap_offset *mmo = area->vm_private_data;
> +	struct drm_i915_gem_object *obj = mmo->obj;
> +	int err = 0;
> +
> +	if (i915_gem_object_is_readonly(obj) && write)
> +		return -EACCES;
> +
> +	addr -= area->vm_start;
> +	if (addr >= obj->base.size)
> +		return -EINVAL;
> +
> +	err = i915_gem_object_lock_interruptible(obj, NULL);
> +	if (err)
> +		return err;
> +
> +	len = ttm_bo_vm_access_reserved(i915_gem_to_ttm(obj), area,
> +					addr, buf, len, write);
> +	i915_gem_object_unlock(obj);
> +
> +	return len;
> +}
> +
> +static const struct vm_operations_struct vm_ops_ttm = {
> +	.fault = vm_fault_ttm,
> +	.access = vm_access_ttm,
> +	.open = i915_gem_mmap_vm_open,
> +	.close = i915_gem_mmap_vm_close,
> +};
> +
> +const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
>   	.name = "i915_gem_object_ttm",
>   	.flags = I915_GEM_OBJECT_HAS_IOMEM,
>   
> @@ -463,6 +565,7 @@ static const struct drm_i915_gem_object_ops i915_gem_ttm_obj_ops = {
>   	.truncate = i915_ttm_purge,
>   	.adjust_lru = i915_ttm_adjust_lru,
>   	.delayed_free = i915_ttm_delayed_free,
> +	.mmap_ops = &vm_ops_ttm,
>   };
>   
>   void i915_ttm_bo_destroy(struct ttm_buffer_object *bo)
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