GEM

mesa

ret = drmIoctl(fd, DRM_IOCTL_AMDGPU_GEM_MMAP, &map);
sim_bo->mmap_offset = map.out.addr_ptr;

sim_bo->gem_vaddr = mmap(NULL, sim_bo->size,PROT_READ | PROT_WRITE, MAP_SHARED,
fd, sim_bo->mmap_offset);

gem ioctl

DRM_IOCTL_DEF_DRV(AMDGPU_GEM_CREATE, amdgpu_gem_create_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),

DRM_IOCTL_DEF_DRV(AMDGPU_GEM_MMAP, amdgpu_gem_mmap_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),

1. amdgpu_gem_create_ioctl 创建一个内存对象，并实例化成一个dma-buf，返回handle

       amdgpu_bo_create_user(adev, &bp, &ubo);
           (*obj)->funcs = &amdgpu_gem_object_funcs;
   

2. amdgpu_gem_mmap_ioctl 拿到内存对象的虚拟地址偏移量
   

   C *offset_p = amdgpu_bo_mmap_offset(robj); drm_vma_node_offset_addr(&bo->tbo.base.vma_node);

3. addr = mmap(NULL, size, PROT_READ | PROT_WRITE, MAP_SHARED, fd, mmap_offset);

   sim_bo->gem_vaddr = mmap(NULL, sim_bo->size, PROT_READ | PROT_WRITE, MAP_SHARED,
                            fd, sim_bo->mmap_offset);
   

   drm_gem_dmabuf_mmap drm_gem_prime_mmap 这个时候，如果在初始化gem_obj的时候设置了mmap函数以及vm_ops，则会调用。其中需要关注的是vm_ops.fault函数amdgpu_gem_fault以及mmap函数amdgpu_gem_object_mmap.

   int drm_gem_prime_mmap(struct drm_gem_object *obj, struct vm_area_struct *vma)
   {
       /* Add the fake offset */
       vma->vm_pgoff += drm_vma_node_start(&obj->vma_node);
   
       if (obj->funcs && obj->funcs->mmap) {
           vma->vm_ops = obj->funcs->vm_ops;
   
           drm_gem_object_get(obj);
           ret = obj->funcs->mmap(obj, vma);
           if (ret) {
               drm_gem_object_put(obj);
               return ret;
           }
           vma->vm_private_data = obj;
           return 0;
       }
   
   }
   

prime import/export

DRM提供了两个ioctl命令，分别对应导入和导出：

DRM_IOCTL_DEF(DRM_IOCTL_PRIME_HANDLE_TO_FD, drm_prime_handle_to_fd_ioctl, DRM_RENDER_ALLOW)

DRM_IOCTL_DEF(DRM_IOCTL_PRIME_FD_TO_HANDLE, drm_prime_fd_to_handle_ioctl, DRM_RENDER_ALLOW)

DMA Fence

DRM_IOCTL_DEF_DRV(AMDGPU_WAIT_CS, amdgpu_cs_wait_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),

DRM_IOCTL_DEF_DRV(AMDGPU_WAIT_FENCES, amdgpu_cs_wait_fences_ioctl, DRM_AUTH|DRM_RENDER_ALLOW),

i915_gem_object_wait_reservation