[BUG] MVPP2 driver exploding in presence of a tap interface

Hi all,

This is a follow-up on the conversation Thomas and I had last week at 
ELC, with me ranting at the sorry state of the MVPP2 driver.

I reported this last time in a conversation on the macchiato list,
but it looks like nobody investigated the issue at the time:

https://lists.einval.com/pipermail/macchiato/2018-January/000085.html

Triggering this is dead simple:
- Add a macvtap to one of the MVPP2 interfaces
- Bring it online
- Watch the kernel exploding and memory being corrupted

You don't even need anything listening on the tap interface, just its
simple existence triggers it. I use a similar setup on a large variety 
of machines, and this box is the only one that catches fire. Removing
the macvtap interface makes it (more) reliable.

Given that I cannot reproduce this issue on any other ARM (32 or 64bit)
platform, including other Marvell stuff, I can only conclude that the
MVPP2 driver is responsible for this.

Example crash and .config below (4.19 vanilla, as linux/master dies in
new and wonderful ways on this box). I'm looking forward to testing any
idea you may have.

	M.

[   29.040686] mvpp2 f2000000.ethernet eth0: Link is Up - 1Gbps/Full - flow control rx/tx
[   29.234413] BUG: Bad page state in process swapper/0  pfn:e6804
[   29.240364] page:ffff7e00039a0100 count:0 mapcount:0 mapping:ffff8000e7bf3800 index:0x0 compound_mapcount: 0
[   29.250238] flags: 0xfffc00000008100(slab|head)
[   29.254793] raw: 0fffc00000008100 dead000000000100 dead000000000200 ffff8000e7bf3800
[   29.262571] raw: 0000000000000000 0000000000100010 00000000ffffffff 0000000000000000
[   29.270345] page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
[   29.276813] bad because of flags: 0x100(slab)
[   29.281190] Modules linked in:
[   29.284264] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.19.0-dirty #272
[   29.290903] Hardware name: Marvell 8040 MACCHIATOBin (DT)
[   29.296323] Call trace:
[   29.298784]  dump_backtrace+0x0/0x148
[   29.302461]  show_stack+0x14/0x20
[   29.305789]  dump_stack+0x90/0xb4
[   29.309117]  bad_page+0x104/0x130
[   29.312444]  free_pages_check_bad+0x9c/0xa8
[   29.316642]  __free_pages_ok+0x1b0/0x450
[   29.320580]  page_frag_free+0x8c/0xa8
[   29.324257]  skb_free_head+0x18/0x30
[   29.327846]  skb_release_data+0x130/0x160
[   29.331870]  skb_release_all+0x24/0x30
[   29.335633]  consume_skb+0x2c/0x58
[   29.339047]  arp_process.constprop.4+0x200/0x6f0
[   29.343681]  arp_rcv+0xf4/0x128
[   29.346834]  __netif_receive_skb_one_core+0x54/0x78
[   29.351731]  __netif_receive_skb+0x14/0x60
[   29.355843]  netif_receive_skb_internal+0x40/0x138
[   29.360653]  napi_gro_receive+0x64/0xc8
[   29.364504]  mvpp2_poll+0x384/0x6b8
[   29.368005]  net_rx_action+0x104/0x2c0
[   29.371768]  __do_softirq+0x10c/0x208
[   29.375444]  irq_exit+0xb8/0xc8
[   29.378597]  __handle_domain_irq+0x64/0xb8
[   29.382709]  gic_handle_irq+0x50/0xa0
[   29.386383]  el1_irq+0xb0/0x128
[   29.389535]  arch_cpu_idle+0x10/0x18
[   29.393124]  do_idle+0x208/0x280
[   29.396363]  cpu_startup_entry+0x24/0x28
[   29.400302]  rest_init+0xd0/0xdc
[   29.403543]  start_kernel+0x3d8/0x400
[   29.407220] Disabling lock debugging due to kernel taint
[   30.578010] BUG: Bad page state in process swapper/0  pfn:e681d
[   30.583963] page:ffff7e00039a0740 count:0 mapcount:0 mapping:ffff8000ef43f080 index:0x0
[   30.592002] flags: 0xfffc00000000100(slab)
[   30.596120] raw: 0fffc00000000100 dead000000000100 dead000000000200 ffff8000ef43f080
[   30.603889] raw: 0000000000000000 00000000001e001e 00000000ffffffff 0000000000000000
[   30.611663] page dumped because: PAGE_FLAGS_CHECK_AT_FREE flag(s) set
[   30.618131] bad because of flags: 0x100(slab)
[   30.622508] Modules linked in:
[   30.625580] CPU: 0 PID: 0 Comm: swapper/0 Tainted: G    B  4.19.0-dirty #272
[   30.633615] Hardware name: Marvell 8040 MACCHIATOBin (DT)
[   30.639035] Call trace:
[   30.641495]  dump_backtrace+0x0/0x148
[   30.645172]  show_stack+0x14/0x20
[   30.648499]  dump_stack+0x90/0xb4
[   30.651826]  bad_page+0x104/0x130
[   30.655153]  free_pages_check_bad+0x9c/0xa8
[   30.659352]  __free_pages_ok+0x1b0/0x450
[   30.663288]  page_frag_free+0x8c/0xa8
[   30.666965]  skb_free_head+0x18/0x30
[   30.670554]  skb_release_data+0x130/0x160
[   30.674578]  skb_release_all+0x24/0x30
[   30.678341]  kfree_skb+0x2c/0x58
[   30.681582]  __udp4_lib_rcv+0x818/0x910
[   30.685432]  udp_rcv+0x1c/0x28
[   30.688498]  ip_local_deliver_finish+0x100/0x248
[   30.693133]  ip_local_deliver+0x60/0x110
[   30.697070]  ip_rcv_finish+0x38/0x50
[   30.700658]  ip_rcv+0x50/0xd8
[   30.703636]  __netif_receive_skb_one_core+0x54/0x78
[   30.708532]  __netif_receive_skb+0x14/0x60
[   30.712643]  netif_receive_skb_internal+0x40/0x138
[   30.717452]  napi_gro_receive+0x64/0xc8
[   30.721302]  mvpp2_poll+0x384/0x6b8
[   30.724803]  net_rx_action+0x104/0x2c0
[   30.728566]  __do_softirq+0x10c/0x208
[   30.732242]  irq_exit+0xb8/0xc8
[   30.735395]  __handle_domain_irq+0x64/0xb8
[   30.739506]  gic_handle_irq+0x50/0xa0
[   30.743182]  el1_irq+0xb0/0x128
[   30.746334]  arch_cpu_idle+0x10/0x18
[   30.749922]  do_idle+0x208/0x280
[   30.753161]  cpu_startup_entry+0x24/0x28
[   30.757099]  rest_init+0xd0/0xdc
[   30.760339]  start_kernel+0x3d8/0x400


-- 
Jazz is not dead. It just smells funny...