[SeaBIOS] [RFC v3] Support multiple pci domain for pxb-pcie of qemu

[Zihan Yang]

The qemu part of this patch can be found in
https://lists.gnu.org/archive/html/qemu-devel/2018-09/msg01988.html

pxb-pcie device in qemu uses only one pci domain(0) so far, which means
there are at most 256 busses. However, pcie topology requires one bus per
device, which will use up the busses soon if there are more pcie devices.

To solve the problem, QEMU can put the pxb-pcie in separate pci domain so
we can get more devices. As QEMU relies on seabios to allocate space for
its mcfg table, we must modify the seabios to configure mcfg_base and
mcfg_size for qemu.

Since pxb-pcie may only uses a subset of all 256 busses in a domain,
we let qemu pass its desired mcfg_size as a hidden bar, seabios just
decides the mcfg_base for it.

Compared with previous design, mmconfig is not put above 4g anymore,
but inside [0x80000000, 0xb0000000), and leaves the major part of
configuration to guest OS, which makes the whole part of code much
simpler.

Changelog:
v3 <- v2
- Refactor design so that seabios only does minimal mcfg configure, and
  leaves everything else to guest os. This makes the code much simpler.
- Does not put mcfg over 4g anymore, but inside [0x80000000, 0xb0000000)
  Over 4g placement can be expected in future version.

v2 <- v1
- Fix bugs in filtering domains when traversing pci devices
- Reformat some hardcoded codes, such as probing the pci device in pci_setup

Zihan Yang (1):
  pciinit: setup mcfg for pxb-pcie to support multiple pci domains

 src/fw/dev-q35.h |  7 +++++++
 src/fw/pciinit.c | 32 ++++++++++++++++++++++++++++++++
 src/hw/pci_ids.h |  1 +
 3 files changed, 40 insertions(+)

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2.7.4