USB disk corruption on Xen 4.1.0 & Linux 2.6.38.7

[Anthony Wright <anthony@overnetdata.com>]

I build Xen 4.1.0 and linux 2.6.38.7 from source to do a DIY system based on Linux From Scratch (LFS).

When I try to read from a USB memory stick (around 64M big), I get corruption on the latest version of Xen.

With Xen 3.x and linux 2.6.18 I can read the memory stick no problems.

If I use the linux 2.6.38.7 kernel without a Xen hypervisor I can read the memory stick without problems.

If I use the same setup, but this time introduce the Xen 4.1.0 hypervisor I get random blocks of sectors on the USB disk returning all zeros. Normally these blocks change each time I reboot, but are fixed once they've been established. On one occasion the blocks changed continuously each time I looked at the disk (I have a big file on the USB disk and I run md5sum before accessing it).

Just to remove other possibilities I've checked the system's RAM and it's fine (I've seen similar problems before with dodgy RAM). If I try to access a hard disk or CDROM, everything is fine.

This could be a problem with the way I've built the kernel or Xen, but it seems to suggest that there's a bug in Xen.

I'm happy to try to isolate the problem further if it can't be reproduced elsewhere. My first suggestion would be to use a known good binary copy of xen 4.1.0 and/or linux 2.6.38.7 if anybody can supply one.

thanks,

Anthony Wright