[Xen-users] Odd domU Reboot Bug (possibly VGA passthrough related)

[Gordan Bobic <gordan@xxxxxxxxxx>]

Diet version:

faux-Quadro 6000 VGA passthrough, works lovely when first started. 
Starting it using this script:
modprobe xen-pciback

# USB Controllers
xl pci-assignable-add 0000:00:1a.0
xl pci-assignable-add 0000:00:1d.2


# Audio
xl pci-assignable-add 0000:0d:00.0

# NIC
xl pci-assignable-add 0000:02:00.0

# GPU
xl pci-assignable-add 0000:0b:00.0
xl pci-assignable-add 0000:0b:00.1

xl create /etc/xen/edi

vinagre :0


But - shut down the domU (XP x64). Start it up again, and:

Jun 30 18:59:08 normandy kernel: irq 18: nobody cared (try booting with 
the "irqpoll" option)
Jun 30 18:59:08 normandy kernel: Pid: 0, comm: swapper/0 Tainted: PF 
      O 3.9.5-1.el6xen.x86_64 #1
Jun 30 18:59:08 normandy kernel: Call Trace:
Jun 30 18:59:08 normandy kernel: NVRM: VM: nv_alloc_contig_pages: failed 
to DMA-map memory
Jun 30 18:59:08 normandy kernel: <IRQ>  [<ffffffff810d416d>] 
__report_bad_irq+0x3d/0xe0
Jun 30 18:59:08 normandy kernel: [<ffffffff810d4366>] 
note_interrupt+0x156/0x210
Jun 30 18:59:08 normandy kernel: [<ffffffff810d1b99>] 
handle_irq_event_percpu+0xc9/0x210
Jun 30 18:59:08 normandy kernel: [<ffffffff810d1d21>] 
handle_irq_event+0x41/0x70
Jun 30 18:59:08 normandy kernel: [<ffffffff810d4a99>] 
handle_fasteoi_irq+0x59/0xf0
Jun 30 18:59:08 normandy kernel: [<ffffffff81302780>] 
__xen_evtchn_do_upcall+0x240/0x380
Jun 30 18:59:08 normandy kernel: [<ffffffff813028ff>] 
xen_evtchn_do_upcall+0x2f/0x50
Jun 30 18:59:08 normandy kernel: [<ffffffff8155c57e>] 
xen_do_hypervisor_callback+0x1e/0x30
Jun 30 18:59:08 normandy kernel: <EOI>  [<ffffffff810013aa>] ? 
xen_hypercall_sched_op+0xa/0x20
Jun 30 18:59:08 normandy kernel: [<ffffffff810013aa>] ? 
xen_hypercall_sched_op+0xa/0x20
Jun 30 18:59:08 normandy kernel: [<ffffffff8100a2a0>] ? 
xen_safe_halt+0x10/0x20
Jun 30 18:59:08 normandy kernel: [<ffffffff8101d166>] ? 
default_idle+0x46/0x100
Jun 30 18:59:08 normandy kernel: [<ffffffff8101ca99>] ? cpu_idle+0xd9/0x120
Jun 30 18:59:08 normandy kernel: [<ffffffff8153a0d5>] ? rest_init+0x75/0x80
Jun 30 18:59:08 normandy kernel: [<ffffffff81801200>] ? 
start_kernel+0x40e/0x41b
Jun 30 18:59:08 normandy kernel: [<ffffffff81800c10>] ? 
repair_env_string+0x5b/0x5b
Jun 30 18:59:08 normandy kernel: [<ffffffff818005f1>] ? 
x86_64_start_reservations+0x2a/0x2c
Jun 30 18:59:08 normandy kernel: [<ffffffff818045ae>] ? 
xen_start_kernel+0x56e/0x570
Jun 30 18:59:08 normandy kernel: handlers:
Jun 30 18:59:08 normandy kernel: [<ffffffff813ca4c0>] usb_hcd_irq
Jun 30 18:59:08 normandy kernel: [<ffffffffa02c3820>] i801_isr [i2c_i801]
Jun 30 18:59:08 normandy kernel: Disabling IRQ #18

This happens reasonably consistently. The domU comes up only in VGA 
16-colour mode on VNC.
But - I've found that shutting it down, doing:
xl mem-set 0 48G
(the machine has 48GB of RAM) makes it work fine again.

IRQ18 is used by two USB controllers (of which one I'm PCI 
passthrough-ing) and a SMBus (i2c_i801) controller.
The thing that bothers me is that NVRM seems to be what's complaining, 
but the GPU being passed through is firmly under control of xen-pciback.
I don't suppose anyone might have an idea on how to gain some useful 
debug info for a bug report out of this?
Gordan

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