[PATCH v6] Fix interrupt latency of HVM PCI passthrough devices.

[Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>]

Changelog:

since v5 (http://lists.xen.org/archives/html/xen-devel/2014-09/msg02868.html)
 - Redid the series based on Jan's feedback
since v4 
(http://lists.xen.org/archives/html/xen-devel/2014-09/msg01676.html):
 - Ditch the domain centric mechansim.
 - Fix issues raised by Jan.

The big change is on ditching of having a domain centric view and
focus on having it all revolve around 'struct hvm_pirq_dpci'
structure. That all works - except that we must be very careful
with the 'dom' field. The patches optimize the mechanism we use
for injecting interrupts in a guest and reduce the latency of
delievering them to a guest.

 xen/arch/x86/domain.c         |   4 +-
 xen/drivers/passthrough/io.c  | 202 ++++++++++++++++++++++++++++++++++++------
 xen/drivers/passthrough/pci.c |  29 ++++--
 xen/include/xen/hvm/irq.h     |   3 +-
 xen/include/xen/pci.h         |   2 +-
 xen/include/xen/softirq.h     |   3 +
 6 files changed, 203 insertions(+), 40 deletions(-)

Konrad Rzeszutek Wilk (3):
      dpci: Move from domain centric model to hvm_dirq_dpci model.
      dpci: In hvm_dirq_assist stop using pt_pirq_iterate
      dpci: Replace tasklet with an softirq (v6)