Xen users - Aug 2008 - kexec regression between 3.1.0 and 3.1.3 ?

Hi there,

There seems to be a regression with regard to kexec''ing into a Xen
kernel
between Xen 3.1.0 (confirmed working) and 3.1.3 (confirmed not working). I
would try 3.1.1 and 3.1.2 but source for 3.1 versions older than 3.1.3 no
longer seems to be available for download. I still had source for 3.1.0 lying
around, luckily.

I''m building and running Xen on 64 bit AMD64 systems.

Basically, up to 3.1.0 I can kexec into a Xen kernel like this:

# kexec --console-vga --console-serial -l /boot/xen-3.1.0.gz
--module="//boot/vmlinuz-2.6.18-xen
root=/dev/sda ro console=tty0 console=ttyS0,115200"
--module="/boot/initrd.img-2.6.18-xen"
--command-line="com1=115200,8n1 cdb=com1"
# kexec -e
>From 3.1.3, this no longer works:
# kexec --console-vga --console-serial -l /boot/xen-3.1.3.gz
--module="//boot/vmlinuz-2.6.18.8-xen
root=/dev/sda ro console=tty0 console=ttyS0,115200"
--module="/boot/initrd.img-2.6.18.8-xen"
--command-line="com1=115200,8n1 cdb=com1"
# kexec -e

Kexec loads the Xen kernel fine, but hangs when trying to execute it.
I''ve
done some digging in the kexec source, and from what I can tell it hangs
sometime after running the __NR_reboot syscall, so presumably somewhere early
in the Xen kernel code.

If I add ''earlyprintk=ttyS0,115200,keep'' to the kernel command
line, I see

[    0.000000] Starting new kernel

and then nothing.

I''m using the latest version of kexec (2.0.0 from
http://www.kernel.org/pub/linux/kernel/people/horms/kexec-tools/), but
I''ve
also tested older kexec versions which behave identically.

I first observed this on real iron, but I''ve now set up a test
environment
with qemu which behaves identical.

Any suggestions?

Thanks,
Ward.

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