A kernel test bot reported a problem with the locktorture testcase that
was triggered by the GEM VRAM helpers.
...
[ 10.004734] RIP: 0010:ttm_bo_validate+0x41/0x141 [ttm]
...
[ 10.015669] ? kvm_sched_clock_read+0x5/0xd
[ 10.016157] ? get_lock_stats+0x11/0x3f
[ 10.016607] drm_gem_vram_pin+0x77/0xa2 [drm_vram_helper]
[ 10.017229] drm_gem_vram_driver_gem_prime_vmap+0xe/0x39 [drm_vram_helper]
[ 10.018015] drm_gem_vmap+0x36/0x43 [drm]
[ 10.018491] drm_client_framebuffer_create+0xc6/0x1ca [drm]
[ 10.019143] drm_fb_helper_generic_probe+0x4c/0x157 [drm_kms_helper]
[ 10.019864] __drm_fb_helper_initial_config_and_unlock+0x307/0x442 [drm_kms_helper]
[ 10.020739] drm_fbdev_client_hotplug+0xc8/0x115 [drm_kms_helper]
[ 10.021442] drm_fbdev_generic_setup+0xc4/0xf1 [drm_kms_helper]
[ 10.022120] bochs_pci_probe+0x123/0x143 [bochs_drm]
[ 10.022688] local_pci_probe+0x34/0x75
[ 10.023127] pci_device_probe+0xf8/0x150A
...
It turns out that the bochs and vbox drivers automatically reserved and
unreserved the BO from within their pin and unpin functions. The other
drivers; ast, hibmc and mgag200; performed reservation explicitly. With the
GEM VRAM conversion, automatic BO reservation within pin and unpin functions
accidentally got lost. So for bochs and vbox, ttm_bo_validate() worked on
unlocked BOs.
This patch set fixes the problem by adding automatic reservation to the
implementation of drm_gem_vram_{pin,unpin,push_to_system}() to fix bochs
and vbox. It removes explicit BO reservation around the pin, unpin and
push-to-system calls in the ast, hibmc and mgag200 drivers.
The only exception is the cursor handling of mgag200. In this case, the
mgag200 driver now calls drm_gem_vram_{pin,unpin}_reserved(), which works
with reserved BOs. The respective code should be refactored in a future
patch to work with the regular pin and unpin functions.
Thomas Zimmermann (2):
drm: Add drm_gem_vram_{pin/unpin}_reserved() and convert mgag200
drm: Reserve/unreserve GEM VRAM BOs from within pin/unpin functions
drivers/gpu/drm/ast/ast_mode.c | 24 +---
drivers/gpu/drm/drm_gem_vram_helper.c | 115 +++++++++++++++++-
.../gpu/drm/hisilicon/hibmc/hibmc_drm_de.c | 6 -
.../gpu/drm/hisilicon/hibmc/hibmc_drm_fbdev.c | 17 +--
drivers/gpu/drm/mgag200/mgag200_cursor.c | 18 +--
drivers/gpu/drm/mgag200/mgag200_mode.c | 19 +--
include/drm/drm_gem_vram_helper.h | 3 +
7 files changed, 126 insertions(+), 76 deletions(-)
--
2.21.0
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