On Tue, May 07, 2024 at 01:04:11PM GMT, Shuicheng Lin wrote:
Here is the failure stack:
[ 12.988209] ------------[ cut here ]------------
[ 12.988216] UBSAN: shift-out-of-bounds in ./include/linux/log2.h:57:13
[ 12.988232] shift exponent 64 is too large for 64-bit type 'long unsigned int'
[ 12.988235] CPU: 4 PID: 1310 Comm: gnome-shell Tainted: G U 6.9.0-rc6+prerelease1158+ #19
[ 12.988237] Hardware name: Intel Corporation Raptor Lake Client Platform/RPL-S ADP-S DDR5 UDIMM CRB, BIOS RPLSFWI1.R00.3301.A02.2208050712 08/05/2022
[ 12.988239] Call Trace:
[ 12.988240] <TASK>
[ 12.988242] dump_stack_lvl+0xd7/0xf0
[ 12.988248] dump_stack+0x10/0x20
[ 12.988250] ubsan_epilogue+0x9/0x40
[ 12.988253] __ubsan_handle_shift_out_of_bounds+0x10e/0x170
[ 12.988260] dma_resv_reserve_fences.cold+0x2b/0x48
[ 12.988262] ? ww_mutex_lock_interruptible+0x3c/0x110
[ 12.988267] drm_exec_prepare_obj+0x45/0x60 [drm_exec]
[ 12.988271] ? vm_bind_ioctl_ops_execute+0x5b/0x740 [xe]
[ 12.988345] vm_bind_ioctl_ops_execute+0x78/0x740 [xe]
It is caused by the value 0 of parameter num_fences in function drm_exec_prepare_obj.
And lead to in function __rounddown_pow_of_two, "0 - 1" causes the shift-out-of-bounds.
ok
For num_fences == 0 case, drm_exec_prepare_obj is the same as drm_exec_lock_obj in
function, so call drm_exec_lock_obj instead to solve it.
this is not true and per discussion in this thread it's not going to
change. drm_exec_prepare_obj() should not be called with num_fences ==
0. So I'd reworded with something like below so we have all breadcrumbs
for anyone trying to understand the changes later:
By design drm_exec_prepare_obj() should be called only when there are
fences to be reserved. If num_fences is 0, calling drm_exec_lock_obj()
is sufficient as was done in commit 9377de4cb3e8 ("drm/xe/vm: Avoid
reserving zero fences")
Cc: Nirmoy Das <nirmoy.das@xxxxxxxxx>
Cc: Matthew Brost <matthew.brost@xxxxxxxxx>
Signed-off-by: Shuicheng Lin <shuicheng.lin@xxxxxxxxx>
with the reword,
Reviewed-by: Lucas De Marchi <lucas.demarchi@xxxxxxxxx>
And also add:
Link: https://lore.kernel.org/all/24d4a9a9-c622-4f56-8672-21f4c6785476@xxxxxxx
Could you also submit a patch to add the warning like mentioned by
Christian?
thanks
Lucas De Marchi
---
drivers/gpu/drm/xe/xe_vm.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/drivers/gpu/drm/xe/xe_vm.c b/drivers/gpu/drm/xe/xe_vm.c
index d17192c8b7de..c5b1694b292f 100644
--- a/drivers/gpu/drm/xe/xe_vm.c
+++ b/drivers/gpu/drm/xe/xe_vm.c
@@ -2692,7 +2692,7 @@ static int vma_lock_and_validate(struct drm_exec *exec, struct xe_vma *vma,
if (bo) {
if (!bo->vm)
- err = drm_exec_prepare_obj(exec, &bo->ttm.base, 0);
+ err = drm_exec_lock_obj(exec, &bo->ttm.base);
if (!err && validate)
err = xe_bo_validate(bo, xe_vma_vm(vma), true);
}
@@ -2777,7 +2777,7 @@ static int vm_bind_ioctl_ops_lock_and_prep(struct drm_exec *exec,
struct xe_vma_op *op;
int err;
- err = drm_exec_prepare_obj(exec, xe_vm_obj(vm), 0);
+ err = drm_exec_lock_obj(exec, xe_vm_obj(vm));
if (err)
return err;
--
2.25.1
