Re: [Qemu-devel] [PATCH 0/4] pc: inform SeaBIOS where 64-bit PCI hole start and PCI mappings cleanup

[Michael S. Tsirkin]

On Wed, Oct 16, 2013 at 10:49:10AM +0200, Igor Mammedov wrote:
> * simplify PCI address space mapping into system address space,
>   replacing code duplication in piix/q53 PCs with helper function

I think this does not go far enough.

I was always wondering about PCI hole in QEMU.
Some real PCs have a "PCI hole" where PCI
masks real memory, but PIIX does not do this,
instead PCI is whenever RAM does not mask it.

So it looks like the hole concept is a left-over
from when we didn't have priorities in the memory API.
How about we remove them?
See patch below.
I did a quick boot test and it seems to work, of course
it needs much more testing.
It's on top of Marcel's series adding negative priorities,
so works on top of the acpi branch or the pci branch.

I'm also wondering about the smram region - it uses
priority 1 but does not say why.
Need to check what does it overlap with, and why.



diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index bad3953..988516a 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -102,8 +102,6 @@ struct PCII440FXState {
     MemoryRegion *system_memory;
     MemoryRegion *pci_address_space;
     MemoryRegion *ram_memory;
-    MemoryRegion pci_hole;
-    MemoryRegion pci_hole_64bit;
     PAMMemoryRegion pam_regions[13];
     MemoryRegion smram_region;
     uint8_t smm_enabled;
@@ -326,7 +324,6 @@ PCIBus *i440fx_init(PCII440FXState **pi440fx_state,
     PCII440FXState *f;
     unsigned i;
     I440FXState *i440fx;
-    uint64_t pci_hole64_size;
 
     dev = qdev_create(NULL, TYPE_I440FX_PCI_HOST_BRIDGE);
     s = PCI_HOST_BRIDGE(dev);
@@ -354,23 +351,9 @@ PCIBus *i440fx_init(PCII440FXState **pi440fx_state,
         i440fx->pci_info.w32.begin = 0xe0000000;
     }
 
-    memory_region_init_alias(&f->pci_hole, OBJECT(d), "pci-hole", 
f->pci_address_space,
-                             pci_hole_start, pci_hole_size);
-    memory_region_add_subregion(f->system_memory, pci_hole_start, 
&f->pci_hole);
-
-    pci_hole64_size = pci_host_get_hole64_size(i440fx->pci_hole64_size);
-
-    pc_init_pci64_hole(&i440fx->pci_info, 0x100000000ULL + above_4g_mem_size,
-                       pci_hole64_size);
-    memory_region_init_alias(&f->pci_hole_64bit, OBJECT(d), "pci-hole64",
-                             f->pci_address_space,
-                             i440fx->pci_info.w64.begin,
-                             pci_hole64_size);
-    if (pci_hole64_size) {
-        memory_region_add_subregion(f->system_memory,
-                                    i440fx->pci_info.w64.begin,
-                                    &f->pci_hole_64bit);
-    }
+    /* Set to lower priority than RAM */
+    memory_region_add_subregion_overlap(f->system_memory, 0x0,
+                                        f->pci_address_space, -1);
     memory_region_init_alias(&f->smram_region, OBJECT(d), "smram-region",
                              f->pci_address_space, 0xa0000, 0x20000);
     memory_region_add_subregion_overlap(f->system_memory, 0xa0000,