[Xen-devel] [RFC 0/7] RFC Linux-based QEMU-upstream stub domain

[Eric Shelton <eshelton@xxxxxxxxx>]

This patch series updates Anthony Perard's original patch series to
bring support for running QEMU upstream as a device model in a
stubdomain by using a Linux-based stubdom, rather than MiniOS as
currently used for QEMU traditional.  Anthony posted the original
patch series on April 17, 2013.

The first three patches build Linux 3.17.8 and a disk image for the
stubdomain itself.  QEMU is being pulled from the same repo as is
being used for Xen 4.5.0, and some minor patches are being applied.
A new directory is created within xen.git, stubdom-linux.  Calling
'make' in this directory will build Linux, QEMU upstream, and an
ext2 disk image.  Then a 'make install' will copy the Linux kernel
and disk image into the same directory used for other stubdomain
images, such as MiniOS.  This build process has by no means been
integrated with the overall Xen build process.  A more refined
process would be expected for release code, such as integration
with configure, eliminating the hard-coded path for 'make install',
and only doing a single download of the QEMU sources.

The last four patches are the libxl support, which allows selecting
between MiniOS/QEMU-traditional and Linux/QEMU-upstream.  For
QEMU-upstream, the VM config file would include:

device_model_version = "qemu-xen" 
device_model_stubdomain_override = 1

For QEMU-traditional, the VM config file would include:

device_model_version = "qemu-xen-traditional" 
device_model_stubdomain_override = 1

There a number of features that are not supported yet:
- video output (e.g., VNC)
- save/restore
- QMP

QMP, or at least part of the QMP protocol, will likely present
some interesting issues.  Assumedly, there will be some subset of
QMP commands that will require some coordination between the QEMU
instance running in the stubdomain and a QEMU instance running in
Dom0 (or some other domain).

Other expected tweaks:
- Currently 128MB of memory is being used for the stubdomain.  This
  is more than needed, but no attempt has been made to find the
  appropriate lower limit.
- The kernel config.
- The disk image can be made smaller.

This patch series has been successfully used to run a simple Linux
HVM guest, without the Xen drivers built into the kernel (this is
not meant to imply that the drivers will not work, but was more to
confirm the emulated NIC and disks provided by QEMU worked).  Once
booted up, it was possible to successfully SSH into the Linux HVM
guest.

Regards,
Eric Shelton

--

Patches:
[RFC 1/7] linux-stubdomain: Compile QEMU
[RFC 2/7] linux-stubdomain: Compile Linux
[RFC 3/7] linux-stubdomain: Build a disk image
[RFC 4/7] libxl: Add "stubdomain_version" to domain_build_info
[RFC 5/7] libxl: Handle Linux stubdomain specific QEMU options
[RFC 6/7] libxl: Build the domain with a Linux based stubdomain
[RFC 7/7] libxl: Wait for QEMU startup in stubdomain


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