linux-kernel - Re: WARNING: CPU: 4 PID: 863 at include/drm/drm_crtc.h:1577 drm_helper_choose_encoder

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Date:	Wed, 23 Sep 2015 18:18:39 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Daniel Vetter <daniel@...ll.ch>,
	Thomas Gleixner <tglx@...utronix.de>
Cc:	Alex Deucher <alexdeucher@...il.com>,
	Alex Deucher <alexander.deucher@....com>,
	Christian König <christian.koenig@....com>,
	Maling list - DRI developers 
	<dri-devel@...ts.freedesktop.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: WARNING: CPU: 4 PID: 863 at include/drm/drm_crtc.h:1577
 drm_helper_choose_encoder_dpms+0x88/0x90()

On Wed, Sep 23, 2015 at 06:06:21PM +0200, Borislav Petkov wrote:
> On Wed, Sep 23, 2015 at 04:44:50PM +0200, Daniel Vetter wrote:
> > sorry I sprinkled the locking stuff in the wrong places. Still confused
> > why the resume side doesn't blow up anywhere
> 
> But it does:
> 
> [   69.394204] BUG: unable to handle kernel NULL pointer dereference at 0000000000000034
> [   69.402080] IP: [<ffffffff81321296>] pci_restore_msi_state+0x196/0x240
> [   69.408624] PGD 4162b8067 PUD 416581067 PMD 0 
> [   69.413122] Oops: 0000 [#1] PREEMPT SMP 
> [   69.417101] Modules linked in: tun sha256_ssse3 sha256_generic drbg binfmt_misc ipv6 vfat fat fuse dm_crypt dm_mod kv
> m_amd kvm crc32_pclmul aesni_intel aes_x86_64 lrw gf128mul glue_helper ablk_helper cryptd amd64_edac_mod edac_mce_amd fa
> m15h_power k10temp amdkfd amd_iommu_v2 radeon acpi_cpufreq
> [   69.443647] CPU: 4 PID: 814 Comm: kworker/u16:5 Not tainted 4.3.0-rc2+ #3
> [   69.450430] Hardware name: To be filled by O.E.M. To be filled by O.E.M./M5A97 EVO R2.0, BIOS 1503 01/16/2013
> [   69.460336] Workqueue: events_unbound async_run_entry_fn
> [   69.465667] task: ffff88042a255f00 ti: ffff880428a68000 task.ti: ffff880428a68000
> [   69.473145] RIP: 0010:[<ffffffff81321296>]  [<ffffffff81321296>] pci_restore_msi_state+0x196/0x240
> [   69.482131] RSP: 0018:ffff880428a6bc28  EFLAGS: 00010286
> [   69.487436] RAX: 0000000000000000 RBX: ffff88042a308000 RCX: 0000000000000000
> [   69.494568] RDX: 0000000000000001 RSI: ffffffff81304448 RDI: ffffffff816c7a1b
> [   69.501700] RBP: ffff880428a6bc40 R08: 0000000000000001 R09: 0000000000522000
> [   69.508833] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
> [   69.515965] R13: ffff88042a3087b0 R14: ffff88042a308010 R15: ffff88042a308038
> [   69.523097] FS:  00007fc91328a700(0000) GS:ffff88042ce00000(0000) knlGS:0000000000000000
> [   69.531185] CS:  0010 DS: 0000 ES: 0000 CR0: 000000008005003b
> [   69.536931] CR2: 0000000000000034 CR3: 00000004164c7000 CR4: 00000000000406e0
> [   69.544061] Stack:
> [   69.546073]  0080002c2a3087b0 0000000000000000 ffff88042a308000 ffff880428a6bc78
> [   69.553525]  ffffffff8130c141 ffff88042a308098 ffff88042a308000 0000000000000000
> [   69.560996]  ffff8804284e77a8 ffffffff81961ef1 ffff880428a6bc88 ffffffff8130c2b8
> [   69.568450] Call Trace:
> [   69.571044]  [<ffffffff8130c141>] pci_restore_state.part.18+0xf1/0x250
> [   69.577706]  [<ffffffff8130c2b8>] pci_restore_state+0x18/0x20
> [   69.583591]  [<ffffffff8130f7fc>] pci_pm_restore_noirq+0x4c/0xd0
> [   69.589734]  [<ffffffff8130f7b0>] ? pci_pm_freeze_noirq+0xf0/0xf0
> [   69.595966]  [<ffffffff8146e847>] dpm_run_callback+0x77/0x2a0
> [   69.601850]  [<ffffffff8146eb03>] device_resume_noirq+0x93/0x150
> [   69.607994]  [<ffffffff8146ebdd>] async_resume_noirq+0x1d/0x50
> [   69.613967]  [<ffffffff81078a06>] async_run_entry_fn+0x46/0xf0
> [   69.619939]  [<ffffffff8106f548>] process_one_work+0x1f8/0x640
> [   69.625910]  [<ffffffff8106f4a4>] ? process_one_work+0x154/0x640
> [   69.632054]  [<ffffffff8106f9db>] worker_thread+0x4b/0x440
> [   69.637677]  [<ffffffff8106f990>] ? process_one_work+0x640/0x640
> [   69.643822]  [<ffffffff81075e86>] kthread+0xf6/0x110
> [   69.648927]  [<ffffffff81075d90>] ? kthread_create_on_node+0x1f0/0x1f0
> [   69.655591]  [<ffffffff816c893f>] ret_from_fork+0x3f/0x70
> [   69.661128]  [<ffffffff81075d90>] ? kthread_create_on_node+0x1f0/0x1f0
> [   69.667794] Code: 66 89 4d ee 0f b7 c9 e8 79 41 fe ff 48 89 df e8 d1 7a ce ff 0f b6 53 4b 8b 73 38 48 8d 4d ee 48 8b 7b 10 83 c2 02 e8 1a 31 fe ff <41> 0f b6 4c 24 34 41 8b 54 24 30 be ff ff ff ff c0 e9 04 83 e1 
> [   69.687986] RIP  [<ffffffff81321296>] pci_restore_msi_state+0x196/0x240
> [   69.694772]  RSP <ffff880428a6bc28>
> [   69.698412] CR2: 0000000000000034
> [   69.701879] ---[ end trace 814dd8cc56e427ae ]---

Ok, after some quick staring, we're at __pci_restore_msi_state():

        pci_read_config_word(dev, dev->msi_cap + PCI_MSI_FLAGS, &control);
        msi_mask_irq(entry, msi_mask(entry->msi_attrib.multi_cap),
                     entry->masked);

which is:

	.loc 1 411 0
	movq	%rbx, %rdi	# dev,
	call	arch_restore_msi_irqs	#
.LBB1921:
.LBB1922:
	.loc 2 902 0
	movzbl	75(%rbx), %edx	# dev_2(D)->msi_cap, D.31945
	movl	56(%rbx), %esi	# MEM[(const struct pci_dev *)dev_2(D)].devfn, MEM[(const struct pci_dev *)dev_2(D)].devfn
	leaq	-18(%rbp), %rcx	#, tmp266
	movq	16(%rbx), %rdi	# MEM[(const struct pci_dev *)dev_2(D)].bus, MEM[(const struct pci_dev *)dev_2(D)].bus
	addl	$2, %edx	#, D.31945
	call	pci_bus_read_config_word	#
.LBE1922:
.LBE1921:
	.loc 1 414 0
	movzbl	52(%r12), %ecx	# *_85, tmp208					<--- faulting insn
	movl	48(%r12), %edx	# _85->D.27233.D.27231.masked, D.31946
.LBB1923:
.LBB1924:
	.loc 1 176 0
	movl	$-1, %esi	#, D.31951

and that %r12 is supposed to contain struct msi_desc *entry in
__pci_restore_msi_state():

	entry = irq_get_msi_desc(dev->irq);

which is

        .loc 4 654 0
        movl    1340(%rdi), %edi        # dev_2(D)->irq, dev_2(D)->irq
        call    irq_get_irq_data        #
        .loc 4 655 0
        testq   %rax, %rax      # d
        je      .L405   #,
        movq    16(%rax), %rax  # d_62->common, d_62->common
        movq    16(%rax), %r12  # _63->msi_desc, D.31954

but as we see above %r12 is 0.

For some reason that entry thing in __pci_restore_msi_state() is not
checked for NULL even though irq_get_msi_desc() can return NULL.

Maybe tglx would have an idea...

Hrmmm.

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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