qemu/docs/pcie_pci_bridge.txt

6 PCIE-to-PCI bridge is a new method for legacy PCI
9 Previously Intel DMI-to-PCI bridge was used for this purpose.
10 But due to its strict limitations - no support of hot-plug,
11 no cross-platform and cross-architecture support - a new generic
12 PCIE-to-PCI bridge should now be used for any legacy PCI device usage
15 This generic PCIE-PCI bridge is a cross-platform device,
16 can be hot-plugged into appropriate root port (requires additional actions,
17 see 'PCIE-PCI bridge hot-plug' section),
18 and supports devices hot-plug into the bridge itself
21 Hot-plug of legacy PCI devices into the bridge
22 is provided by bridge's built-in Standard hot-plug Controller.
25 PCIE-PCI bridge hot-plug
27 Guest OSes require extra efforts to enable PCIE-PCI bridge hot-plug.
28 Motivation - now on init any PCI Express root port which doesn't have
30 to a hot-plugged devices in future.
35 Red Hat vendor-specific PCI capability, added to the root port
36 that is planned to have PCIE-PCI bridge hot-plugged in.
42     uint8_t len;    Standard PCI vendor-specific capability header field
44     uint8_t type;   Red Hat vendor-specific capability type
52     uint32_t mem           Non-prefetchable memory to reserve
55     different from -1:
56     uint32_t mem_pref_32;  Prefetchable memory to reserve (32-bit MMIO)
57     uint64_t mem_pref_64;  Prefetchable memory to reserve (64-bit MMIO)
59 If any reservation field is -1 then this kind of reservation is not
63 (-device pcie-root-port). Capability construction function takes all reservation
65 set to -1 to leave root port's default behavior unchanged.
71 [qemu-bin + storage options] \
72 -m 2G \
73 -device pcie-root-port,bus=pcie.0,id=rp1,slot=1 \
74 -device pcie-root-port,bus=pcie.0,id=rp2,slot=2 \
75 -device pcie-root-port,bus=pcie.0,id=rp3,slot=3,bus-reserve=1 \
76 -device pcie-pci-bridge,id=br1,bus=rp1 \
77 -device pcie-pci-bridge,id=br2,bus=rp2 \
78 -device e1000,bus=br1,addr=8
81 device_add pcie-pci-bridge,id=br3,bus=rp3 \
86  (1) Cold-plugged:
87     - Root ports: 1 QEMU generic root port with the capability mentioned above,
89     - 2 PCIE-PCI bridges plugged into 2 different root ports;
90     - e1000 plugged into the first bridge.
91  (2) Hot-plugged:
92     - PCIE-PCI bridge, plugged into QEMU generic root port;
93     - 2 e1000 cards, one plugged into the cold-plugged PCIE-PCI bridge,
94                      another plugged into the hot-plugged bridge.
98 The PCIE-PCI bridge can be hot-plugged only into pcie-root-port that
99 has proper 'bus-reserve' property value to provide secondary bus for the
100 hot-plugged bridge.
102 Windows 7 and older versions don't support hot-plug devices into the PCIE-PCI bridge.
103 To enable device hot-plug into the bridge on Linux there're 3 ways:
104 1) Build shpchp module with this patch http://www.spinics.net/lists/linux-pci/msg63052.html
106 3) Set 'msi' property to off - this forces the bridge to use legacy INTx,
107     which allows the bridge to notify the OS about hot-plug event without having
112 The PCIE-PCI bridge is based on PCI-PCI bridge, but also accumulates PCI Express