[XenAccess-devel] Towards HVM support

[Steve B. <st...@at...>]

I previously reported on this list that xenaccess-0.1 with libvirt-0.1.1 did
not work with Xen HVM guests.  Here is the error it generated at the time:

# ./run ./module-list
libvir: Xen Daemon error : internal error domain information incomplete,
missing kernel
ERROR: failed to get domain info for domain id 1
ERROR: could not get kernel name for domain id 1
failed to init XenAccess library: bad address


Now I'm trying XenAccess 0.2 along with libvirt-0.1.3.  Since libvirt states
the following about HVM domains, I was hoping things would work.  Here are
the relevant changes from the libvirt changelog:

* docs/format.html docs/libvir.html docs/news.html: updated the XML
  format documentation to cover the new HVM domains.

* src/xend_internal.c src/xml.c: patches from Jim Fehlig for HVM
  guests, plus XML format changes and merge from Mark McLoughlin


However, rebuilding libvirt and xenaccess I get a new error:

# ./run ./module-list 8
Entity: line 7: parser error : Unescaped '<' not allowed in attributes
values
    <boot dev='/dev/cdro  </os>
                          ^
Entity: line 7: parser error : attributes construct error
    <boot dev='/dev/cdro  </os>
                          ^
Entity: line 7: parser error : Couldn't find end of Start Tag boot line 7
    <boot dev='/dev/cdro  </os>
                          
ERROR: could not parse xml data for domain id 8
ERROR: could not get kernel name for domain id 8
ERROR: failed to lookup 'swapper_pg_dir' address
failed to init XenAccess library: Bad address


Now we're getting closer.  I fixed a bug in a libvirt source file
(xend_internal.c) and got a bit further:

# ./run ./module-list 8
ERROR: could not get kernel name for domain id 8
ERROR: failed to lookup 'swapper_pg_dir' address
failed to init XenAccess library: Bad address


So I modifed xenaccess's file linux_domain_info.c to account for hvms,
knowing I was running vmlinuz-2.6.17 inside my VM:

# ./run ./module-list 8
ERROR: failed to lookup 'swapper_pg_dir' address
failed to init XenAccess library: Bad address


Now we're getting into stuff I can't easily understand.  I have no idea if
an how we're getting a hold of the guest's System.map-2.6.17 file.  And if
we are, I don't know if or how we're getting the address for swapper_pg_dir.

I'm not looking for a general solution just yet.  I simply want to
proof-of-concept the ability to get module lists from an HVM.  Bryan, can
you give me any ideas on how to proceed?  I'm attaching an .rtf that, if
opened in MS Word, compares the xml formats for paravirtualized and hvms,
for what it's worth.  Oh, and thanks for version 0.2!

Thanks,

Steve Brueckner, ATC-NY