[Qemu-devel] [PATCH RFC 0/3] pci: complete master abort protocol

[Marcel Apfelbaum <marcel.a@redhat.com>]

Note: The series is incomplete, for review only

PCI spec requires that a transaction that has not been claimed
by any PCI bus devices will be terminated by the initiator
with "master abort". For read transactions -1(FFFFFFFF) is returned and 
writes are silently dropped. (already implemented in quemu)

The series deals with the other aspect of the master abort scenario:
Upon completion the master has to raise MASTER ABORT BIT in i
initiator's STATUS register.

Implementation:
Allowed the MemoryRegion  priority to be negative so a subregion will be
visible on all the addresses not covered by the parent MemoryRegion
or other subregions.
Added a memory region with negative priority that extends over all the
pci address space. This region catches all the accesses
to the unassigned pci addresses.
The MeomoryRegion's ops callbacks emulate the master abort scenario.

Note:
For the moment the code assumes that all the reads/writes on
pci address space are done by the cpu.

Marcel Apfelbaum (3):
  memory: allow MemoryRegion's priority field to accept negative values
  hw/pci: add MemoryRegion ops for unassigned pci addresses
  hw/pci-host: catch acesses to unassigned pci addresses

 hw/pci-host/piix.c        |  8 ++++++++
 hw/pci-host/q35.c         | 19 ++++++++++++++++---
 hw/pci/pci.c              | 18 ++++++++++++++++++
 include/exec/memory.h     |  6 +++---
 include/hw/pci-host/q35.h |  1 +
 include/hw/pci/pci.h      |  3 +++
 memory.c                  |  2 +-
 7 files changed, 50 insertions(+), 7 deletions(-)

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1.8.3.1