[Xen-bugs] [Bug 549] New: Reboot of DomU on different CPU then Dom0 causes DomU panic

[bugzilla-daemon@xxxxxxxxxxxxxxxxxxx]

http://bugzilla.xensource.com/bugzilla/show_bug.cgi?id=549

           Summary: Reboot of DomU on different CPU then Dom0 causes DomU
                    panic
           Product: Xen
           Version: unstable
          Platform: x86-64
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P2
         Component: Unspecified
        AssignedTo: xen-bugs@xxxxxxxxxxxxxxxxxxx
        ReportedBy: japh@xxxxxxxxxx


When I initiate a reboot from within the DomU on a domain that is running on a
CPU that isn't the one Dom0 is running on, I repeatably get:

....
md: Autodetecting RAID arrays.    
md: autorun ...               
md: ... autorun DONE.
VFS: Cannot open root device "sda1" or unknown-block(0,0)
Please append a correct "root=" boot option              
Kernel panic - not syncing: VFS: Unable to mount root fs on unknown-block(0,0)

It appears that this is the old xenstore device setup race, which is solved for
rebooting domains on the same CPU as Dom0 (as Dom0 actually has to steal some of
that CPU), but not for domains on a fully independant CPU.

I can 100% repeat this in my environment with both domains on CPU1

vcpu-list

Name                              ID  VCPU  CPU  State  Time(s)  CPU Affinity
Domain-0                           0     0    0   r--     718.6  any cpu
Domain-0                           0     1    -   --p       0.0  any cpu
Mandriva2006                       2     0    0   -b-     934.6  any cpu
Mandriva2006-32                    6     0    0   ---       4.0  any cpu
FedoraCore4-32                     8     0    1   -b-      21.0  any cpu
Ubuntu                             9     0    1   -b-       2.3  any cpu

(note the -32 indicates a 64bit domU kernel with a 32bit userspace)

Host information:

system                 : Linux
host                   : hermes.pok.ibm.com
release                : 2.6.16-rc4-xen0
version                : #1 Fri Feb 24 14:25:07 EST 2006
machine                : x86_64
nr_cpus                : 2
nr_nodes               : 1
sockets_per_node       : 1
cores_per_socket       : 2
threads_per_core       : 1
cpu_mhz                : 1989
hw_caps                :
178bfbff:ebd3fbff:00000000:00000010:00002001:00000000:ffffffff
total_memory           : 1983
free_memory            : 638
xen_major              : 3
xen_minor              : 0
xen_extra              : .0
xen_caps               : xen-3.0-x86_64 hvm-3.0-x86_32 hvm-3.0-x86_64
platform_params        : virt_start=0xffff800000000000
xen_changeset          : Fri Feb 24 16:37:09 2006 +0100 8961:0807931dfa54
cc_compiler            : gcc version 4.0.1 (4.0.1-5mdk for Mandriva Linux
release 2006.0
cc_compile_by          : sdague
cc_compile_domain      : pok.ibm.com
cc_compile_date        : Fri Feb 24 14:16:47 EST 2006

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