[RFC PATCH v2 08/11] hw/pci-host/raven: Remove pointless alias mapping onto system bus

[Philippe Mathieu-Daudé]

The 'pci-io' alias (mapped with priority 0) ends up masked by
the 'pci-io-non-contiguous' I/O region (mapped with priority 1).

The flatview rendering is ('pci-io-non-contiguous' is written
'pci-io-nc'):

(base addr) [               MemoryRegion               ]        [   FlatView   ]

           +----------------------------+---------------+
           |         priority 0         |   priority 1  |
           +----------------------------+---------------+

8000.0000  +-            +--------------+---------------+      +---------------+
                         |   "pci-io"   |  "pci-io-nc"  |      |  "pci-io-nc"  |
                         |              |               |      |               |
                         | / - isadev   |               |      |               |
                         | | - isadev   |               |      |               |
                         | | - isadev   |               +----> |               |
                         | \ - isadev   |               |      |               |
                         |              |               |      |               |
                         |              |               |      |               |
                         |              |               |      |               |
8080.0000  +-------------+              +---------------+      +---------------+
           |   "pciio"   |              |                      |    "pciio"    |
           |             |              |                      |               |
           |             |              |                      |               |
           |             +  -  -  -  -  |--------------------> |               |
           |             |              |                      |               |
           |             |              |                      |               |
           |             |              |                      |               |
80c0.0000  +-------------+              |                      +---------------+
                         |              |                       +-------------+
                         |              |                       |    "???"    |
                         |              |                       |             |
                         |              |        ???????----->  | unassigned? |
                         |              |                       |             |
                         |              |                       |             |
                         |              |                       |             |
bf80.0000  +-            +--------------+                       +-------------+

The before/after this commit memory tree diff is:

  (qemu) info mtree
  memory-region: system
    0000000000000000-ffffffffffffffff (prio 0, i/o): system
      0000000000000000-0000000001ffffff (prio 0, ram): simm.0
      0000000002000000-0000000003ffffff (prio 1, ram): simm.1
      0000000004000000-0000000005ffffff (prio 2, ram): simm.2
      0000000006000000-0000000007ffffff (prio 3, ram): simm.3
      0000000080000000-00000000807fffff (prio 1, i/o): pci-io-non-contiguous
-     0000000080000000-00000000bf7fffff (prio 0, i/o): alias pci-io @pci-io 
0000000000000000-000000003f7fffff
      0000000080800000-0000000080bfffff (prio 0, i/o): pciio
      00000000bfffeff0-00000000bfffeff3 (prio 0, i/o): ppc-parity
      00000000bffffff0-00000000bffffff0 (prio 0, i/o): pci-intack
      00000000c0000000-00000000feffffff (prio 0, i/o): pci-memory
        00000000c00a0000-00000000c00bffff (prio 1, i/o): vga-lowmem
      00000000f0000510-00000000f0000511 (prio 0, i/o): fwcfg.ctl
      00000000f0000512-00000000f0000512 (prio 0, i/o): fwcfg.data
      00000000fff00000-00000000ffffffff (prio 0, rom): bios

We can see it in the monitor, before/after this patch, the
flatview rendering is left unchanged (note the unassigned
80c0.0000-bf7f.ffff range):

  (qemu) info mtree  -f
  FlatView #1
   AS "memory", root: system
   AS "cpu-memory-0", root: system
   Root memory region: system
    0000000000000000-0000000001ffffff (prio 0, ram): simm.0
    0000000002000000-0000000003ffffff (prio 1, ram): simm.1
    0000000004000000-0000000005ffffff (prio 2, ram): simm.2
    0000000006000000-0000000007ffffff (prio 3, ram): simm.3
    0000000080000000-00000000807fffff (prio 1, i/o): pci-io-non-contiguous
    0000000080800000-0000000080bfffff (prio 0, i/o): pciio
    00000000bfffeff0-00000000bfffeff3 (prio 0, i/o): ppc-parity
    00000000bffffff0-00000000bffffff0 (prio 0, i/o): pci-intack
    00000000c00a0000-00000000c00bffff (prio 1, i/o): vga-lowmem
    00000000f0000510-00000000f0000511 (prio 0, i/o): fwcfg.ctl
    00000000f0000512-00000000f0000512 (prio 0, i/o): fwcfg.data
    00000000fff00000-00000000ffffffff (prio 0, rom): bios

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
RFC because I can't justify the unassigned 80c0.0000-bf7f.ffff range.
---
 hw/pci-host/raven.c | 7 +------
 1 file changed, 1 insertion(+), 6 deletions(-)

diff --git a/hw/pci-host/raven.c b/hw/pci-host/raven.c
index 7bbb7ef0a29..f9c92b83770 100644
--- a/hw/pci-host/raven.c
+++ b/hw/pci-host/raven.c
@@ -67,7 +67,6 @@ struct PRePPCIState {
     PCIBus pci_bus;
     AddressSpace pci_io_as;
     MemoryRegion pci_io;
-    MemoryRegion pci_io_alias;
     MemoryRegion pci_io_non_contiguous;
     MemoryRegion pci_memory;
     MemoryRegion pci_intack;
@@ -299,8 +298,6 @@ static void raven_pcihost_initfn(Object *obj)
     DeviceState *pci_dev;
 
     memory_region_init(&s->pci_io, obj, "pci-io", 0x3f800000);
-    memory_region_init_alias(&s->pci_io_alias, obj, "pci-io",
-                             &s->pci_io, 0, memory_region_size(&s->pci_io));
     memory_region_init_io(&s->pci_io_non_contiguous, obj, &raven_io_ops, s,
                           "pci-io-non-contiguous", 0x00800000);
     memory_region_init(&s->pci_memory, obj, "pci-memory", 0x3f000000);
@@ -308,9 +305,7 @@ static void raven_pcihost_initfn(Object *obj)
 
     /* CPU address space */
     memory_region_add_subregion(address_space_mem, PCI_IO_BASE_ADDR,
-                                &s->pci_io_alias);
-    memory_region_add_subregion_overlap(address_space_mem, PCI_IO_BASE_ADDR,
-                                        &s->pci_io_non_contiguous, 1);
+                                &s->pci_io_non_contiguous);
     memory_region_add_subregion(address_space_mem, 0xc0000000, &s->pci_memory);
     pci_root_bus_new_inplace(&s->pci_bus, sizeof(s->pci_bus), DEVICE(obj), 
NULL,
                              &s->pci_memory, &s->pci_io, 0, TYPE_PCI_BUS);
-- 
2.26.3