[Intel-gfx] [PATCH] drm/i915: More vma fixups around unbind/destroy

Thu Aug 22 11:55:21 CEST 2013

The important bugfix here is that we must not unlink the vma when
we keep it around as a placeholder for the execbuf code. Since then we
won't find it again when execbuf gets interrupt and restarted and
create a 2nd vma. And since the code as-is isn't fit yet to deal with
more than one vma, hilarity ensues.

Specifically the dma map/unmap of the sg table isn't adjusted for
multiple vmas yet and will blow up like this:

Aug 15 20:12:37 x-ivb9 kernel: [ 8081.750976] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751021] IP: [<ffffffffa008fb37>] i915_gem_gtt_finish_object+0x73/0xc8 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751073] PGD 56bb5067 PUD ad3dd067 PMD 0
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751096] Oops: 0000 [#1] SMP
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751114] Modules linked in: tcp_lp ppdev parport_pc lp parport ipv6 dm_mod dcdbas snd_hda_codec_hdmi pcspkr snd_hda_codec_realtek serio_raw i2c_i801 iTCO_wdt iTCO_vendor_support snd_hda_intel snd_hda_codec lpc_ich snd_hwdep mfd_core snd_pcm snd_page_alloc snd_timer snd soundcore acpi_cpufreq i915 video button drm_kms_helper drm mperf freq_table
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751291] CPU: 1 PID: 16650 Comm: fbo-maxsize Not tainted 3.11.0-rc4_nightlytop_d93f59_debug_20130814_+ #6957
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751334] Hardware name: Dell Inc. OptiPlex 9010/03JR84, BIOS A01 05/04/2012
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751365] task: ffff8800563b3f00 ti: ffff88004bdf4000 task.ti: ffff88004bdf4000
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751396] RIP: 0010:[<ffffffffa008fb37>]  [<ffffffffa008fb37>] i915_gem_gtt_finish_object+0x73/0xc8 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751446] RSP: 0018:ffff88004bdf5958  EFLAGS: 00010246
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751469] RAX: 0000000000000000 RBX: ffff8801135e0000 RCX: ffff8800ad3bf8e0
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751499] RDX: ffff8800ad3bf8e0 RSI: 0000000000000000 RDI: ffff8801007ee780
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751529] RBP: ffff88004bdf5978 R08: ffff8800ad3bf8e0 R09: 0000000000000000
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751559] R10: ffffffff86ca1810 R11: ffff880036a17101 R12: ffff8801007ee780
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751589] R13: 0000000000018001 R14: ffff880118c4e000 R15: ffff8801007ee780
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751619] FS:  00007f401a0ce740(0000) GS:ffff88011e280000(0000) knlGS:0000000000000000
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751653] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751677] CR2: 0000000000000008 CR3: 000000005635c000 CR4: 00000000001407e0
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751707] Stack:
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751717]  ffff8801007ee780 ffff88005c253180 0000000000018000 ffff8801135e0000
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751752]  ffff88004bdf59a8 ffffffffa0088e55 0000000000000011 ffff8801007eec00
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751788]  0000000000018000 ffff880036a17101 ffff88004bdf5a08 ffffffffa0089026
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751823] Call Trace:
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751843]  [<ffffffffa0088e55>] i915_vma_unbind+0xdf/0x1ab [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751875]  [<ffffffffa0089026>] __i915_gem_shrink+0x105/0x177 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751909]  [<ffffffffa0089452>] i915_gem_object_get_pages_gtt+0x108/0x309 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751947]  [<ffffffffa0085ba9>] i915_gem_object_get_pages+0x61/0x90 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.751983]  [<ffffffffa008f22b>] ? gen6_ppgtt_insert_entries+0x103/0x125 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752019]  [<ffffffffa008a113>] i915_gem_object_pin+0x1fa/0x5df [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752054]  [<ffffffffa008cdfe>] i915_gem_execbuffer_reserve_object.isra.6+0x8d/0x1bc [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752094]  [<ffffffffa008d156>] i915_gem_execbuffer_reserve+0x229/0x367 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752131]  [<ffffffffa008dbf6>] i915_gem_do_execbuffer.isra.12+0x4dc/0xf3a [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752166]  [<ffffffff810fc823>] ? might_fault+0x40/0x90
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752195]  [<ffffffffa008eb89>] i915_gem_execbuffer2+0x187/0x222 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752231]  [<ffffffffa000971c>] drm_ioctl+0x308/0x442 [drm]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752261]  [<ffffffffa008ea02>] ? i915_gem_execbuffer+0x3ae/0x3ae [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752292]  [<ffffffff817db156>] ? __do_page_fault+0x3dd/0x481
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752318]  [<ffffffff8112fdba>] vfs_ioctl+0x26/0x39
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752341]  [<ffffffff811306a2>] do_vfs_ioctl+0x40e/0x451
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752366]  [<ffffffff817deda7>] ? sysret_check+0x1b/0x56
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752391]  [<ffffffff8113073c>] SyS_ioctl+0x57/0x87
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752415]  [<ffffffff8135bbfe>] ? trace_hardirqs_on_thunk+0x3a/0x3f
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752443]  [<ffffffff817ded82>] system_call_fastpath+0x16/0x1b
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752469] Code: 48 c7 c6 84 30 0e a0 31 c0 e8 d0 e9 f7 ff bf c6 a7 00 00 e8 07 af 2c e1 41 f6 84 24 03 01 00 00 10 75 44 49 8b 84 24 08 01 00 00 <8b> 50 08 48 8b 30 49 8b 86 b0 04 00 00 48 89 c7 48 81 c7 98 00
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.752624] RIP  [<ffffffffa008fb37>] i915_gem_gtt_finish_object+0x73/0xc8 [i915]
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.753750]  RSP <ffff88004bdf5958>
Aug 15 20:12:37 x-ivb9 kernel: [ 8081.754851] CR2: 0000000000000008

The second thing to correct is the "only one vma for now" check in
vma_unbind - since vma_destroy isn't always called the obj->vma_list
might not be empty. Instead check that the vma list is singular at the
beginning of vma_unbind. This is also more symmetric with bind_to_vm.

Our first attempting at fixing this was

commit 1be81a2f2cfd8789a627401d470423358fba2d76
Author: Chris Wilson <chris at chris-wilson.co.uk>
Date:   Tue Aug 20 12:56:40 2013 +0100

    drm/i915: Don't destroy the vma placeholder during execbuffer reservation

Cc: Chris Wilson <chris at chris-wilson.co.uk>
Cc: Ben Widawsky <ben at bwidawsk.net>
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68298
Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=68171
Signed-off-by: Daniel Vetter <daniel.vetter at ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem.c | 15 +++++++--------
 1 file changed, 7 insertions(+), 8 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index ef92c69..3e855ff 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2616,6 +2616,9 @@ int i915_vma_unbind(struct i915_vma *vma)
 	drm_i915_private_t *dev_priv = obj->base.dev->dev_private;
 	int ret;
 
+	/* For now we only ever use 1 vma per object */
+	WARN_ON(!list_is_singular(&obj->vma_list));
+
 	if (list_empty(&vma->vma_link))
 		return 0;
 
@@ -2661,12 +2664,12 @@ int i915_vma_unbind(struct i915_vma *vma)
 	drm_mm_remove_node(&vma->node);
 
 destroy:
-	i915_gem_vma_destroy(vma);
+	/* Keep the vma as a placeholder in the execbuffer reservation lists */
+	if (!list_empty(&vma->exec_list))
+		i915_gem_vma_destroy(vma);
 
 	/* Since the unbound list is global, only move to that list if
-	 * no more VMAs exist.
-	 * NB: Until we have real VMAs there will only ever be one */
-	WARN_ON(!list_empty(&obj->vma_list));
+	 * no more VMAs exist. */
 	if (list_empty(&obj->vma_list))
 		list_move_tail(&obj->global_list, &dev_priv->mm.unbound_list);
 
@@ -4171,10 +4174,6 @@ void i915_gem_vma_destroy(struct i915_vma *vma)
 	WARN_ON(vma->node.allocated);
 	list_del(&vma->vma_link);
 
-	/* Keep the vma as a placeholder in the execbuffer reservation lists */
-	if (!list_empty(&vma->exec_list))
-		return;
-
 	kfree(vma);
 }
 
-- 
1.8.4.rc3


