Centos 7 gnome-shell high CPU on VirtualBox

top shows very high CPU usage. and UI is very very slow.

googling around, they say it's probably doing "software" rendering. it makes sense because CPU goes higher when I move something on the screen

in /var/log/Xorg.0.log I find this:

(EE) Failed to load module "vboxvideo" (module does not exist, 0)
(II) AIGLX: Screen 0 is not DRI2 capable
(EE) AIGLX: reverting to software rendering


To investigate, I run
sudo glxinfo
sudo lshw -C video
sudo yum list | grep libnvidia
sudo yum list | grep libegl


the output of glxinfo is

name of display: :0
display: :0  screen: 0
direct rendering: Yes
server glx vendor string: Chromium
server glx version string: 1.3 Chromium
server glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, 
    GLX_EXT_texture_from_pixmap, GLX_SGIX_fbconfig
client glx vendor string: Chromium
client glx version string: 1.3 Chromium
client glx extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, 
    GLX_EXT_texture_from_pixmap, GLX_SGIX_fbconfig
GLX version: 1.3
GLX extensions:
    GLX_ARB_get_proc_address, GLX_ARB_multisample, 
    GLX_EXT_texture_from_pixmap, GLX_SGIX_fbconfig
OpenGL vendor string: Humper
OpenGL renderer string: Chromium
OpenGL version string: 2.1 Chromium 1.9
OpenGL shading language version string: 4.30 - Build 10.18.15.4248
OpenGL extensions:
    GL_ARB_depth_texture, GL_ARB_draw_buffers, GL_ARB_fragment_program, 
    GL_ARB_fragment_shader, GL_ARB_multisample, GL_ARB_multitexture, 
    GL_ARB_occlusion_query, GL_ARB_pixel_buffer_object, 
    GL_ARB_point_parameters, GL_ARB_point_sprite, GL_ARB_shader_objects, 
    GL_ARB_shading_language_100, GL_ARB_shadow, GL_ARB_texture_border_clamp, 
    GL_ARB_texture_compression, GL_ARB_texture_cube_map, 
    GL_ARB_texture_env_add, GL_ARB_texture_env_combine, 
    GL_ARB_texture_env_crossbar, GL_ARB_texture_env_dot3, 
    GL_ARB_texture_float, GL_ARB_texture_mirrored_repeat, 
    GL_ARB_texture_non_power_of_two, GL_ARB_texture_rectangle, 
    GL_ARB_transpose_matrix, GL_ARB_vertex_buffer_object, 
    GL_ARB_vertex_program, GL_ARB_vertex_shader, GL_ARB_window_pos, 
    GL_CR_bounding_box, GL_CR_cursor_position, GL_CR_head_spu_name, 
    GL_CR_performance_info, GL_CR_print_string, GL_CR_readback_barrier_size, 
    GL_CR_saveframe, GL_CR_server_id_sharing, GL_CR_server_matrix, 
    GL_CR_state_parameter, GL_CR_synchronization, GL_CR_tile_info, 
    GL_CR_tilesort_info, GL_CR_window_size, GL_EXT_blend_color, 
    GL_EXT_blend_equation_separate, GL_EXT_blend_func_separate, 
    GL_EXT_blend_minmax, GL_EXT_blend_subtract, GL_EXT_clip_volume_hint, 
    GL_EXT_compiled_vertex_array, GL_EXT_draw_range_elements, 
    GL_EXT_fog_coord, GL_EXT_framebuffer_blit, GL_EXT_framebuffer_object, 
    GL_EXT_multi_draw_arrays, GL_EXT_secondary_color, GL_EXT_shadow_funcs, 
    GL_EXT_stencil_two_side, GL_EXT_stencil_two_side, GL_EXT_stencil_wrap, 
    GL_EXT_texture3D, GL_EXT_texture_compression_s3tc, 
    GL_EXT_texture_edge_clamp, GL_EXT_texture_env_add, 
    GL_EXT_texture_env_combine, GL_EXT_texture_filter_anisotropic, 
    GL_EXT_texture_lod_bias, GL_EXT_texture_rectangle, GL_EXT_texture_sRGB, 
    GL_IBM_texture_mirrored_repeat, GL_NV_texgen_reflection, 
    GL_SGIS_generate_mipmap, GL_SGIS_texture_edge_clamp

1 GLX Visuals
    visual  x   bf lv rg d st  colorbuffer  sr ax dp st accumbuffer  ms  cav
  id dep cl sp  sz l  ci b ro  r  g  b  a F gb bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------------
0x021 24 tc  0  32  0 r  y y   8  8  8  8 .  .  0 24  8 16 16 16 16  0 0 None

1 GLXFBConfigs:
    visual  x   bf lv rg d st  colorbuffer  sr ax dp st accumbuffer  ms  cav
  id dep cl sp  sz l  ci b ro  r  g  b  a F gb bf th cl  r  g  b  a ns b eat
----------------------------------------------------------------------------
0x021 24 tc  0  32  0 r  y .   8  8  8  8 .  .  0 24  8  0  0  0  0  1 1 None

On VirtualBox, 3D acceleration is enabled.

So far no clue... the world of Linux Video drivers is amazingly complex... too complex for a simple human like me...