Created attachment 178164 [details]
screenshot of crash

This bug is occuring on this hardware:

- Supermicro X11SAT-F motherboard
- Sky Intel Xeon CPU

I have an aft xm-37u usb 3.0 card reader.

http://www.kioskreader.com/products-xm37u

This card reader seems to work fine if I connect it to the system after I've booted.

When I plug this card reader into one of the internal ports of my motherboard and try to boot the system however, I get a crash in the boot loader. If I remove this device, the system boots fine. I'm using 2 ssds mirrored in zfs as my boot drives on the motherboard's internal sata ports.

First, I see a bunch of gptzfsboot errors like the below:

gptzfsboot error 49 lba 1
gptzfsboot error 49 lba 32
gptzfsboot error 49 lba 1
gptzfsboot error 49 lba 32
gptzfsboot error 49 lba 1
gptzfsboot error 49 lba 32
gptzfsboot error 49 lba 1
gptzfsboot error 49 lba 32
gptzfsboot error 49 lba 1
gptzfsboot error 49 lba 32

and then finally ending in a crash with BTX halted (see attached screenshot).

When I plug in the device, I see all of the various sd card ports show up as 5 bootable drives in the BIOS. You can also see the in the screenshot that the bootloader has detected 14 BIOS drives, whereas normally this system has only 9.

I suspect perhaps the bootloader is somehow getting confused by the presence of these extra drives? I'm pretty sure those 5 pairs of gptzfsboot errors must be getting triggered from the 5 bios drives of the card reader. 

I also tried inserting an sd card into one of the slots of the card reader and rebooting. With the sd card inserted, I get only 4 pairs of gptzfsboot errors instead of 5! Maybe the error is being caused by these memory card ports not having actual disks in them and that is somehow confusing the bootloader?

Also the card reader appears to work fine if plugged in after booting, so the error must be solely related to the bootloader and its interaction with the bios.