Date: Fri, 09 Jul 2010 22:27:46 -0400 From: Boris Kochergin <spawk@acm.poly.edu> To: Hans Petter Selasky <hselasky@c2i.net> Cc: sbruno@freebsd.org, freebsd-current@freebsd.org Subject: Re: QEMU/KVM Panic on USB Mount Message-ID: <4C37DAA2.6080102@acm.poly.edu> In-Reply-To: <201007100016.29946.hselasky@c2i.net> References: <1278695579.2436.27.camel@localhost.localdomain> <201007100016.29946.hselasky@c2i.net>
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Hans Petter Selasky wrote: > On Friday 09 July 2010 19:12:59 Sean Bruno wrote: > >> In order to come up with the most convoluted problem possible, I present >> to you screen shots of a panic from a FreeBSD VM running in QEMU >> emulation under RedHat's KVM infrastructure. >> >> I presented a perfectly functional USB partition from my host machine to >> the VM. Then I attempted to mount the partition from FreeBSD and it >> generated the panics located here: >> >> http://people.freebsd.org/~sbruno/usb_panic1.png >> http://people.freebsd.org/~sbruno/usb_panic2.png >> >> This is 100% reproducible. But not an emergency or anything. >> > > It might be that there is a conflict that both the VM and the OS is accessing > / loading drivers on the same USB device. The panic seems not directly related > to USB. > > --HPS > > I followed the code for a while and the cause of the panic appears to be that ffs_vgetf() in /usr/src/sys/ufs/ffs/ffs_vfsops.c fails in one of the several ways possible, causing in VFS_ROOT() in /usr/src/sys/kern/vfs_mount.c to return a non-zero value and resulting in the panic. I think the problem calls for someone with serious VFS chops. The I/O errors from the USB device are suspicious (in that they may cause the mount code to misbehave if they occur during its course). -Boris
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