pci: honor PCI_COMMAND_MASTERmemory/dma

Currently we ignore PCI_COMMAND_MASTER completely: DMA succeeds even when
the bit is clear.

Honor PCI_COMMAND_MASTER by inserting a memory region into the device's
bus master address space, and tying its enable status to PCI_COMMAND_MASTER.

Tested using

  setpci -s 03 COMMAND=3

while a ping was running on a NIC in slot 3.  The kernel (Linux) detected
the stall and recovered after the command

  setpci -s 03 COMMAND=7

was issued.

Signed-off-by: Avi Kivity <avi@redhat.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/hw/pci.h b/hw/pci.h
index f9207ca06..1f902f5b5 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -212,6 +212,7 @@ struct PCIDevice {
     char name[64];
     PCIIORegion io_regions[PCI_NUM_REGIONS];
     AddressSpace bus_master_as;
+    MemoryRegion bus_master_enable_region;
     DMAContext *dma;
 
     /* do not access the following fields */