Hi Shuah,

FYI, your debug commit

commit 224d4b5563b005836628b1c02ebe374684df118f
Author: Shuah Khan <shuah.khan@hp.com>
Date:   Fri Oct 12 15:23:05 2012 +1100

    dma-debug: new interfaces to debug dma mapping errors

triggers the below warning. Hopefully you know better than me the real
issue and relevant developers to CC.

[   12.756348] IPv6: ADDRCONF(NETDEV_CHANGE): eth0: link becomes ready
[   12.763446] ------------[ cut here ]------------
[   12.764380] WARNING: at /c/kernel-tests/src/stable/lib/dma-debug.c:948 check_unmap+0x645/0x7bd()
[   12.764380] Hardware name: Bochs
[   12.764380] Sending DHCP requests .
[   12.764380] e1000 0000:00:03.0: DMA-API: device driver failed to check map error[device address=0x00000000199140fa] [size=90 bytes] [mapped as single]
[   12.764380] Modules linked in:
[   12.764380] Pid: 0, comm: swapper/1 Not tainted 3.6.0-next-20121012 #1039
[   12.764380] Call Trace:
[   12.764380]  <IRQ>  [<ffffffff8145b79d>] ? check_unmap+0x645/0x7bd
[   12.764380]  [<ffffffff8106c814>] warn_slowpath_common+0x83/0x9c
[   12.764380]  [<ffffffff8106c8d0>] warn_slowpath_fmt+0x46/0x48
[   12.764380]  [<ffffffff8145b79d>] check_unmap+0x645/0x7bd
[   12.764380]  [<ffffffff8105e19b>] ? kvm_clock_read+0x2e/0x36
[   12.764380]  [<ffffffff8145b9da>] debug_dma_unmap_page+0x5b/0x65
[   12.764380]  [<ffffffff8105ecb9>] ? pvclock_clocksource_read+0x4d/0xc3
[   12.764380]  [<ffffffff810a13df>] ? sched_clock_local+0x12/0x75
[   12.764380]  [<ffffffff81721aee>] e1000_unmap_and_free_tx_resource.isra.27+0xc0/0xed
[   12.764380]  [<ffffffff81721bea>] e1000_clean+0xcf/0x73e
[   12.764380]  [<ffffffff8105ecb9>] ? pvclock_clocksource_read+0x4d/0xc3
[   12.764380]  [<ffffffff818fe001>] ? net_rx_action+0x1cc/0x244
[   12.764380]  [<ffffffff818fdefa>] net_rx_action+0xc5/0x244
[   12.764380]  [<ffffffff810740c8>] __do_softirq+0xf6/0x231
[   12.764380]  [<ffffffff81a5f151>] ? _raw_spin_unlock+0x29/0x3d
[   12.764380]  [<ffffffff81a67b3c>] call_softirq+0x1c/0x30
[   12.764380]  [<ffffffff8103c108>] do_softirq+0x4a/0xa6
[   12.764380]  [<ffffffff81074331>] irq_exit+0x51/0xbc
[   12.764380]  [<ffffffff81a6829d>] do_IRQ+0x9d/0xb4
[   12.764380]  [<ffffffff81a5f672>] common_interrupt+0x72/0x72
[   12.764380]  <EOI>  [<ffffffff810a15c8>] ? local_clock+0x1d/0x5a
[   12.764380]  [<ffffffff8105e364>] ? native_safe_halt+0x6/0x8
[   12.764380]  [<ffffffff810c2431>] ? trace_hardirqs_on+0xd/0xf
[   12.764380]  [<ffffffff8104177c>] default_idle+0xc7/0x218
[   12.764380]  [<ffffffff810421e3>] cpu_idle+0x9f/0xf9
[   12.764380]  [<ffffffff81a3f2cb>] start_secondary+0x238/0x240

Thanks,
Fengguang