Revert "drm/i915: Fix context/engine cleanup order"
This reverts commit
1803c035efb88afb9d3e7feb279ac29a83216382.
It seems to blow up on module unload due to a use-after free hitting a
BUG_ON with CONFIG_DEBUG_SG. Quoting from Tvrtko's mail:
"I've decoded the instructions and it pointed to SG_MAGIC checking:
488b8098010000 mov 0x198(%rax),%rax
ba21436587 mov $0x87654321,%edx
488b00 mov (%rax),%rax *** CRASH
"Grep showed 0x87654321 is SG_MAGIC, so likely candidate for this code
pattern is:
static inline struct page *sg_page(struct scatterlist *sg)
{
BUG_ON(sg->sg_magic != SG_MAGIC);
BUG_ON(sg_is_chain(sg));
return (struct page *)((sg)->page_link & ~0x3);
}
"Which would mean the offender is in intel_logical_ring_cleanup is most
likely:
...
if (ring->status_page.obj) {
kunmap(sg_page(ring->status_page.obj->pages->sgl));
ring->status_page.obj = NULL;
}
...
"I think that the i915_gem_context_fini will do a final unref on
dev_priv->kernel_context and then the ring buff has a copy which is
left dangling because:
lrc_setup_hardware_status_page(ring,
dev_priv->kernel_context->engine[ring->id].state);
and:
ring->status_page.obj = default_ctx_obj;
"Where default_ctx_obj == dev_priv->kernel_context->engine[ring->id].state
So indeed looks like the unload ordering is the trigger. In fact it
is almost the same fragility wrt/ kernel_context hidden dependency I
expressed my worry about in an e-mail yesterday or so. It only shows
if CONFIG_DEBUG_SG is set, otherwise it accesses freed memory and
probably just survives."
This causes serious trouble in our CI system since it took out all
gen8+ machines. Not yet clear why this wasn't caught in pre-merge
testing.
Backtrace from CI, for posterity:
[ 163.737836] general protection fault: 0000 [#1] PREEMPT SMP
[ 163.737849] Modules linked in: ax88179_178a usbnet mii snd_hda_codec_hdmi snd_hda_codec_realtek snd_hda_codec_generic i915(-) x86_pkg_temp_thermal intel_powerclamp coretemp crct10dif_pclmul crc32_pclmul ghash_clmulni_intel snd_hda_codec snd_hwdep snd_hda_core snd_pcm mei_me mei i2c_hid e1000e ptp pps_core [last unloaded: snd_hda_intel]
[ 163.737902] CPU: 0 PID: 5812 Comm: rmmod Tainted: G U W 4.5.0-rc1-gfxbench+ #1
[ 163.737911] Hardware name: System manufacturer System Product Name/Z170M-PLUS, BIOS 0505 11/16/2015
[ 163.737920] task:
ffff8800bb99cf80 ti:
ffff88022ff2c000 task.ti:
ffff88022ff2c000
[ 163.737928] RIP: 0010:[<
ffffffffa018f723>] [<
ffffffffa018f723>] intel_logical_ring_cleanup+0x83/0x100 [i915]
[ 163.737969] RSP: 0018:
ffff88022ff2fd30 EFLAGS:
00010282
[ 163.737975] RAX:
6b6b6b6b6b6b6b6b RBX:
ffff8800bb2f31b8 RCX:
0000000000000002
[ 163.737982] RDX:
0000000087654321 RSI:
000000000000000d RDI:
ffff8800bb2f31f0
[ 163.737989] RBP:
ffff88022ff2fd40 R08:
0000000000000000 R09:
0000000000000001
[ 163.737996] R10:
0000000000000000 R11:
0000000000000000 R12:
ffff8800bb2f0000
[ 163.738003] R13:
ffff8800bb2f8fc8 R14:
ffff8800bb285668 R15:
000055af1ae55210
[ 163.738010] FS:
00007f187014b700(0000) GS:
ffff88023bc00000(0000) knlGS:
0000000000000000
[ 163.738021] CS: 0010 DS: 0000 ES: 0000 CR0:
0000000080050033
[ 163.738030] CR2:
0000558f84e4cbc8 CR3:
000000022cd55000 CR4:
00000000003406f0
[ 163.738039] DR0:
0000000000000000 DR1:
0000000000000000 DR2:
0000000000000000
[ 163.738048] DR3:
0000000000000000 DR6:
00000000fffe0ff0 DR7:
0000000000000400
[ 163.738057] Stack:
[ 163.738062]
ffff8800bb2f31b8 ffff8800bb2f0000 ffff88022ff2fd70 ffffffffa0180414
[ 163.738079]
ffff8800bb2f0000 ffff8800bb285668 ffff8800bb2856c8 ffffffffa0242460
[ 163.738094]
ffff88022ff2fd98 ffffffffa0202d30 ffff8800bb285668 ffff8800bb285668
[ 163.738109] Call Trace:
[ 163.738140] [<
ffffffffa0180414>] i915_gem_cleanup_engines+0x34/0x60 [i915]
[ 163.738185] [<
ffffffffa0202d30>] i915_driver_unload+0x150/0x270 [i915]
[ 163.738198] [<
ffffffff815100f4>] drm_dev_unregister+0x24/0xa0
[ 163.738208] [<
ffffffff815106ce>] drm_put_dev+0x1e/0x60
[ 163.738225] [<
ffffffffa01412a0>] i915_pci_remove+0x10/0x20 [i915]
[ 163.738237] [<
ffffffff8143d9b4>] pci_device_remove+0x34/0xb0
[ 163.738249] [<
ffffffff81533d15>] __device_release_driver+0x95/0x140
[ 163.738259] [<
ffffffff81533eb6>] driver_detach+0xb6/0xc0
[ 163.738268] [<
ffffffff81532de3>] bus_remove_driver+0x53/0xd0
[ 163.738278] [<
ffffffff815348d7>] driver_unregister+0x27/0x50
[ 163.738289] [<
ffffffff8143ca15>] pci_unregister_driver+0x25/0x70
[ 163.738299] [<
ffffffff81511de4>] drm_pci_exit+0x74/0x90
[ 163.738337] [<
ffffffffa02034a9>] i915_exit+0x20/0x1a5 [i915]
[ 163.738349] [<
ffffffff8110400f>] SyS_delete_module+0x18f/0x1f0
[ 163.738361] [<
ffffffff817b8a9b>] entry_SYSCALL_64_fastpath+0x16/0x73
[ 163.738370] Code: ff d0 48 89 df e8 de a1 fd ff 48 8d 7b 38 e8 25 ab fd ff 48 8b 83 90 00 00 00 48 85 c0 74 25 48 8b 80 98 01 00 00 ba 21 43 65 87 <48> 8b 00 48 39 10 75 3c f6 40 08 01 75 38 48 c7 83 90 00 00 00
[ 163.738459] RIP [<
ffffffffa018f723>] intel_logical_ring_cleanup+0x83/0x100 [i915]
[ 163.738498] RSP <
ffff88022ff2fd30>
[ 163.738507] ---[ end trace
68f69ce4740fa44f ]---
Cc: Nick Hoath <nicholas.hoath@intel.com>
Cc: Dave Gordon <david.s.gordon@intel.com>
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Tested-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>