While trying to track down some crashes on my Fiji I enabled UBSAN and got this, this led me to look at the function mentioned, and wow totally undefined code land.
The code loops over num_shader_engines with i, then uses i * 16 in a calc for a left-shift. On Fiji at least num_shader_engines is 4, so clearly we are going to see shifts > 32 with that.
The userspace ABI seems limited to a 32-bit value as well here, which to me seems to point out something stinks in either the UABI design or the calculations here.
Dave.
[ 733.803161] ================================================================================ [ 733.803169] UBSAN: Undefined behaviour in /home/airlied/devel/kernel/linux-2.6/drivers/gpu/drm/amd/amdgpu/gfx_v8_0.c:5188:29 [ 733.803172] shift exponent 32 is too large for 32-bit type 'unsigned int' [ 733.803176] CPU: 0 PID: 1787 Comm: Xorg Not tainted 4.6.0-rc6+ #94 [ 733.803178] Hardware name: Gigabyte Technology Co., Ltd. GA-A75M-UD2H/GA-A75M-UD2H, BIOS F6 09/28/2012 [ 733.803180] 0000000000000000 ffff880232753a78 ffffffff814628e5 0000000000000006 [ 733.803184] ffff880232753aa0 0000000000000003 ffff880232753a90 ffffffff814a5ce9 [ 733.803188] ffffffffa0390e5e ffff880232753b30 ffffffff814a6576 0000000000000202 [ 733.803191] Call Trace: [ 733.803198] [<ffffffff814628e5>] dump_stack+0x68/0x99 [ 733.803200] [<ffffffff814a5ce9>] ubsan_epilogue+0xd/0x3a [ 733.803203] [<ffffffff814a6576>] __ubsan_handle_shift_out_of_bounds+0x11f/0x148 [ 733.803207] [<ffffffff81003233>] ? syscall_trace_enter_phase2+0x240/0x3a9 [ 733.803210] [<ffffffff818b1cb1>] ? _raw_spin_unlock_irqrestore+0x3a/0x48 [ 733.803268] [<ffffffffa02bb9f2>] gfx_v8_0_get_cu_info+0x22b/0x2d1 [amdgpu] [ 733.803318] [<ffffffffa02bb9f2>] ? gfx_v8_0_get_cu_info+0x22b/0x2d1 [amdgpu] [ 733.803363] [<ffffffffa022357c>] amdgpu_info_ioctl+0xe91/0xf64 [amdgpu] [ 733.803405] [<ffffffffa0094442>] drm_ioctl+0x379/0x524 [drm] [ 733.803408] [<ffffffff815c88d3>] ? __pm_runtime_resume+0x84/0x91 [ 733.803452] [<ffffffffa02226eb>] ? amdgpu_debugfs_cleanup+0x6/0x6 [amdgpu] [ 733.803456] [<ffffffff810f234b>] ? trace_hardirqs_on_caller+0x1f8/0x227 [ 733.803458] [<ffffffff810f2387>] ? trace_hardirqs_on+0xd/0xf [ 733.803503] [<ffffffffa021e191>] amdgpu_drm_ioctl+0x99/0xe1 [amdgpu] [ 733.803506] [<ffffffff8127d3ab>] vfs_ioctl+0x5a/0x6f [ 733.803508] [<ffffffff8127dbcf>] do_vfs_ioctl+0x724/0x7bb [ 733.803511] [<ffffffff813d3b1a>] ? security_file_ioctl+0x43/0x57 [ 733.803514] [<ffffffff8128bdcd>] ? __fget_light+0xca/0x111 [ 733.803516] [<ffffffff8127dcb8>] SyS_ioctl+0x52/0x74 [ 733.803518] [<ffffffff810035f9>] do_syscall_64+0x85/0x12c [ 733.803521] [<ffffffff818b231a>] entry_SYSCALL64_slow_path+0x25/0x25 [ 733.803523] ============================================================================= ~ ~ ~