kern/49154: Can't find boot device if net-booted from sk(4) gigabit ethernet, prompts for root device

[jdbaker%mylinuxisp.com@localhost]

>Number:         49154
>Category:       kern
>Synopsis:       Can't find boot device if net-booted from sk(4) gigabit 
>ethernet, prompts for root device
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Aug 26 12:50:00 +0000 2014
>Originator:     John D. Baker
>Release:        NetBSD/i386-7.99.1
>Organization:
>Environment:
NetBSD plexor 7.99.1 NetBSD 7.99.1 (PLEXOR) #6: Sun Aug 24 20:23:32 CDT 2014  
sysop%verthandi.technoskunk.fur@localhost:/d0/build/current/obj/i386/sys/arch/i386/compile/PLEXOR
 i386

>Description:
When netbooting a system with an sk(4) PCI gigabit ethernet card, the
kernel is unable to find the boot device and subsequently prompts user
for the root device, etc.

Excerpts from 'dmesg':

NetBSD 7.99.1 (PLEXOR) #6: Sun Aug 24 20:23:32 CDT 2014
        
sysop%verthandi.technoskunk.fur@localhost:/d0/build/current/obj/i386/sys/arch/i386/compile/PLEXOR
total memory = 510 MB
avail memory = 492 MB
kern.module.path=/stand/i386/7.99.1/modules
timecounter: Timecounters tick every 10.000 msec
userconf: configure system autoconfiguration:
uc> disable eap
[ 88] eap* disabled
uc> exit
Continuing...
timecounter: Timecounter "i8254" frequency 1193182 Hz quality 100
Dell Computer Corporation OptiPlex GX110               
[...]
skc0 at pci1 dev 10 function 0: irq 9
skc0: interrupt moderation is 0 us
skc0: 3Com Gigabit NIC (3C2000) rev. (0x1)
sk0 at skc0 port A: Ethernet address 00:0a:5e:24:c2:08
makphy0 at sk0 phy 0: Marvell 88E1011 Gigabit PHY, rev. 3
makphy0: 10baseT, 10baseT-FDX, 100baseTX, 100baseTX-FDX, 1000baseT, 
1000baseT-FDX, auto
[...]
IPsec: Initialized Security Association Processing.
Kernelized RAIDframe activated
findroot: netboot interface not found.
findroot: netboot interface not found.
boot device: <unknown>
root device: sk0
dump device: 
file system (default generic): 
root on sk0
nfs_boot: trying DHCP/BOOTP
skc0: interrupt moderation is 1000 us
ehci0: unrecoverable error, controller halted
ehci0: blocking intrs 0x10


On the machine from which these logs were taken, having the sk(4) card
installed appears to interfere with an eap(4) audio card such that the
machine panics during boot.  That driver was disabled to permit the
boot to proceed.  It appears to also adversely affect the USB portion
of a USB2/Firewire card also installed in the machine.  The ehci(4)
driver would sometimes report "strange port".  Both of these issues
are subjects for their own PRs as the rootdev behavior has been observed
on another machine using this card, but with no ill side-effects.

(This machine was available for testing while the other is not.)
>How-To-Repeat:
Attempt to netboot/NFS-root a machine using an sk(4) card as shown
above.
>Fix: