[PATCH v4 0/8] Support for running secondary emulators

[Paul Durrant <paul.durrant@citrix.com>]

This patch series adds the ioreq server interface which I mentioned in
my talk at the Xen developer summit in Edinburgh at the end of last year.
The code is based on work originally done by Julien Grall but has been
re-written to allow existing versions of QEMU to work unmodified.

The code is available in my xen.git [1] repo on xenbits, under the 'savannah4'
branch, and I have also written a demo emulator to test the code, which can
be found in my demu.git [2] repo.


The series has been re-worked since v3. The modifications are now broken
down as follows:

Patch #1 is a pre-series tidy-up. No semantic change.

Patch #2 moves some code around to centralize use of the ioreq_t data
structure.

Patch #3 introduces the new hvm_ioreq_server structure.

Patch #4 defers creation of the ioreq server until something actually
reads one of the HVM parameters concerned with emulation.

Patch #5 makes the single ioreq server of previous patches into the
default ioreq server and introduces an API for creating secondary servers.

Patch #6 adds an enable/disable operation to the API for secondary servers
which makes sure that they cannot be active whilst their shared pages are
present in the guest's P2M.

Patch #7 adds makes handling bufferd ioreqs optional for secondary servers.
This saves a page of memory.

Patch #8 pulls the PCI hotplug controller emulation into Xen. This is
necessary to allow a secondary emulator to hotplug a PCI device into the VM.
The code implements the controller in the same way as upstream QEMU and thus
the variant of the DSDT ASL used for upstream QEMU is retained.


The demo emulator can simply be invoked from a shell and will hotplug its
device onto the PCI bus (and remove it again when it's killed). The emulated
device is not an awful lot of use at this stage - it appears as a SCSI
controller with one IO BAR and one MEM BAR and has no intrinsic
functionality... but then it is only supposed to be demo :-)

  Paul

[1] http://xenbits.xen.org/gitweb/?p=people/pauldu/xen.git
[2] http://xenbits.xen.org/gitweb/?p=people/pauldu/demu.git

v2:
 - First non-RFC posting

v3:
 - Addressed comments from Jan Beulich

v4:
 - Addressed comments from Ian Campbell and George Dunlap
 - Series heavily re-worked, 2 patches added