I've found some mistakes in my configuration of the linux kernel, and I can load those modules(xen-gntdev, xen-gntalloc, xen-evtchn) now.
And I've fixed the problem of missing scsi devices under /sys/bus/scsi/devices/ directory. I learned that /etc/init.d/xencommons should be started before starting xend.
 
I'll try to create new pv guests next step.
Thank you for your help.
 
One more question:
Does missing block device backend driver cause any problem?
 
 
2011-04-21
Wishes
Ruozeng W 
发件人： Konrad Rzeszutek Wilk
发送时间： 2011-04-19  21:33:45
收件人： ruozeng.w
抄送： xen-devel
主题： Re: Re: Re: [Xen-devel] Xend cannot start
On Tue, Apr 19, 2011 at 10:56:25AM +0800, ruozeng.w wrote:
> I got the 2.6.39-rc3 kernel full source from http://www.kernel.org.
The 2.6.39-rc3 does not have the blkback driver in. There is a version
git://git.kernel.org/pub/scm/linux/kernel/git/konrad/xen.git #master
that has that one.
> And CONFIG_PARAVIRT is turned on.
Ok, so that is there.
> 
> Here is the steps I configure the kernel:
> 1. Processor type and features
> High Memory Support--->
> 64GB
> (Then I can see PAE and some xen related options)
OK, so you have the right version of Dom0. What about the version of
Xen-unstable? Are you compiling it from scratch?