intel-iommu/vfio-pci: crash in dmar_insert_dev_info

[Jan Kiszka]

Hi Alex,

starting to play with Intel IGD pass-through in KVM, I managed to
trigger this with linux git head:

[  232.317043] BUG: unable to handle kernel NULL pointer dereference at 0000000000000037
[  232.325249] IP: [<ffffffff8142ed36>] dmar_insert_dev_info+0x86/0x220
[  232.331905] PGD 0 
[  232.334007] Oops: 0000 [#1] PREEMPT SMP 
[  232.338118] Modules linked in: vfio_iommu_type1 vfio_pci vfio af_packet x86_pkg_temp_thermal coretemp kvm_intel kvm crc32_pclmul eeepc_wmi crc32c_intel e1000e asus_wmi sparse_keymap ghash_clmulni_intel i2c_i801 video aesni_intel xhci_x
[  232.384673] CPU: 1 PID: 3770 Comm: qemu-system-x86 Not tainted 3.19.0-rc6+ #23
[  232.392234] Hardware name: ASUS All Series/H87I-PLUS, BIOS 0306 04/15/2013
[  232.399431] task: ffff8800c7fda350 ti: ffff8800c562c000 task.ti: ffff8800c562c000
[  232.407265] RIP: 0010:[<ffffffff8142ed36>]  [<ffffffff8142ed36>] dmar_insert_dev_info+0x86/0x220
[  232.416470] RSP: 0018:ffff8800c562fc48  EFLAGS: 00010086
[  232.422027] RAX: 0000000000000286 RBX: ffff8800cc4ea0c0 RCX: 0000000000000286
[  232.429498] RDX: ffffffffffffffff RSI: ffff88011fa5a748 RDI: ffffffff81f917ac
[  232.436977] RBP: ffff8800c562fc88 R08: ffff88011a5c0140 R09: 0000000000000001
[  232.444447] R10: ffff88011abfa400 R11: ffffea0003dab4c0 R12: ffff88011a5c0140
[  232.451918] R13: 0000000000000000 R14: 0000000000000010 R15: ffff88011a405098
[  232.459389] FS:  00007f4d4093d900(0000) GS:ffff88011fa40000(0000) knlGS:0000000000000000
[  232.467860] CS:  0010 DS: 0000 ES: 0000 CR0: 0000000080050033
[  232.473874] CR2: 0000000000000037 CR3: 00000000c8281000 CR4: 00000000001427e0
[  232.481344] DR0: 0000000000000000 DR1: 0000000000000000 DR2: 0000000000000000
[  232.488813] DR3: 0000000000000000 DR6: 00000000fffe0ff0 DR7: 0000000000000400
[  232.496282] Stack:
[  232.498380]  ffff88011a405000 ffff88011b317100 ffff88011b317100 ffff88011a405098
[  232.506137]  ffff88011a405098 ffff88011a5c0140 0000000000000000 ffff8800c7f48c58
[  232.513893]  ffff8800c562fcd8 ffffffff8143061c ffffffff81420cd0 ffff88011f0db4c0
[  232.521650] Call Trace:
[  232.524207]  [<ffffffff8143061c>] domain_add_dev_info+0x4c/0xa0
[  232.530404]  [<ffffffff81420cd0>] ? iommu_attach_device+0xb0/0xb0
[  232.536783]  [<ffffffff81430bb4>] intel_iommu_attach_device+0x144/0x1e0
[  232.543710]  [<ffffffff81420cd0>] ? iommu_attach_device+0xb0/0xb0
[  232.550089]  [<ffffffff81420c40>] iommu_attach_device+0x20/0xb0
[  232.556285]  [<ffffffff81420ce2>] iommu_group_do_attach_device+0x12/0x20
[  232.563301]  [<ffffffff81420f5a>] iommu_group_for_each_dev+0x4a/0x80
[  232.569952]  [<ffffffff81420fc9>] iommu_attach_group+0x19/0x20
[  232.576058]  [<ffffffffa0271a74>] vfio_iommu_type1_attach_group+0x184/0x470 [vfio_iommu_type1]
[  232.585077]  [<ffffffff811a2410>] ? kmem_cache_alloc_trace+0x1b0/0x1c0
[  232.591912]  [<ffffffffa01d8750>] vfio_fops_unl_ioctl+0x1e0/0x2b0 [vfio]
[  232.598930]  [<ffffffff811c7a4e>] do_vfs_ioctl+0x7e/0x550
[  232.604580]  [<ffffffff811d1984>] ? __fget+0x74/0xb0
[  232.609776]  [<ffffffff811c7fb1>] SyS_ioctl+0x91/0xb0
[  232.615062]  [<ffffffff816512ad>] system_call_fastpath+0x16/0x1b
[  232.621348] Code: 28 4c 89 60 38 48 8b 45 c8 48 89 43 30 e8 b3 21 22 00 4d 85 ff 0f 84 fa 00 00 00 49 8b 97 30 02 00 00 48 85 d2 0f 84 aa 00 00 00 <4c> 8b 6a 38 4d 85 ed 74 41 48 89 c6 48 c7 c7 ac 17 f9 81 e8 62 
[  232.641335] RIP  [<ffffffff8142ed36>] dmar_insert_dev_info+0x86/0x220
[  232.648082]  RSP <ffff8800c562fc48>
[  232.651728] CR2: 0000000000000037
[  232.655193] ---[ end trace 31cafba6f4a5aab8 ]---


What I did was to apply [1] to overrule the RMRR check, prepared the
qemu and seabios versions as suggested in [2], and then gave the
chipset's igd of a H87I-PLUS board to qemu:

qemu-system-x86_64 -machine q35,accel=kvm -cpu host -acpitable \
  file=qemu/pc-bios/q35-acpi-dsdt.aml -m 2G \
  -device vfio-pci,host=00:02.0,id=vga1,x-vga=on,addr=2.0,romfile=vbios.dump \
  -vga none -net none...

But even if userspace is totally broken, that oops should not happen, I
guess...

Will try an older kernel now, but let me know if I should look into
anything on the crashing setup.

Jan

[1] https://git.outsideglobe.com/igdvfio/linux-igdvfio/commit/2ae1675e3ac86c1dc6e81816748d41cb7d216a9d
[2] https://github.com/UmbraMalison/qemu-igdvfio

-- 
Siemens AG, Corporate Technology, CT RTC ITP SES-DE
Corporate Competence Center Embedded Linux
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