Bug#696292: For 9p root filesystems, kernel ignores root=$NAME option on command line, and uses /dev/root as mount tag

[Josh Triplett <josh@joshtriplett.org>]

Package: src:linux
Version: 3.6.9-1~experimental.1
Severity: normal

The virtio 9p filesystem uses a "mount tag" to distinguish between
multiple filesystems provided to the guest.  The host can provide these
via the mount_tag=$NAME parameter to kvm's -virtfs option, and the guest
supplies the mount tag as the device name to mount.  This works fine for
non-root filesystems.  However, when attempting to use a virtio 9p
filesystem as the root filesystem (with rootfstype=9p), the kernel
ignores the "root=$NAME" option on the kernel command line, and always
uses "/dev/root" as the mount tag.  Making matters worse, kvm itself
doesn't currently accept "/dev/root" as a mount tag, or anything else
with a '/' in it (separate bug filed for that).  Hacking kvm to accept
/dev/root allows this to work, but the kernel really should use the name
passed to the root= option as the mount tag.

- Josh Triplett

-- System Information:
Debian Release: 7.0
  APT prefers unstable
  APT policy: (500, 'unstable'), (1, 'experimental')
Architecture: amd64 (x86_64)

Kernel: Linux 3.6-trunk-amd64 (SMP w/4 CPU cores)
Locale: LANG=C.UTF-8, LC_CTYPE=C.UTF-8 (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash

Versions of packages linux-image-3.6-trunk-amd64 depends on:
ii  debconf [debconf-2.0]                   1.5.48
ii  initramfs-tools [linux-initramfs-tool]  0.109
ii  kmod                                    9-2
ii  linux-base                              3.5
ii  module-init-tools                       9-2

Versions of packages linux-image-3.6-trunk-amd64 recommends:
pn  firmware-linux-free  <none>

Versions of packages linux-image-3.6-trunk-amd64 suggests:
pn  debian-kernel-handbook  <none>
ii  grub-pc                 1.99-23.1
pn  linux-doc-3.6           <none>

Versions of packages linux-image-3.6-trunk-amd64 is related to:
pn  firmware-atheros        <none>
pn  firmware-bnx2           <none>
pn  firmware-bnx2x          <none>
pn  firmware-brcm80211      <none>
pn  firmware-intelwimax     <none>
pn  firmware-ipw2x00        <none>
pn  firmware-ivtv           <none>
ii  firmware-iwlwifi        0.36
pn  firmware-libertas       <none>
pn  firmware-linux          <none>
pn  firmware-linux-nonfree  <none>
pn  firmware-myricom        <none>
pn  firmware-netxen         <none>
pn  firmware-qlogic         <none>
ii  firmware-ralink         0.33
pn  firmware-realtek        <none>
pn  xen-hypervisor          <none>

-- debconf information excluded