hw/pci/pci_bridge.c - qemu - Git at Google

 /*
  * QEMU PCI bus manager
  *
  * Copyright (c) 2004 Fabrice Bellard
  *
  * Permission is hereby granted, free of charge, to any person obtaining a copy
  * of this software and associated documentation files (the "Software"), to dea

  * in the Software without restriction, including without limitation the rights
  * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  * copies of the Software, and to permit persons to whom the Software is
  * furnished to do so, subject to the following conditions:
  *
  * The above copyright notice and this permission notice shall be included in
  * all copies or substantial portions of the Software.
  *
  * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
  * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM

  * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  * THE SOFTWARE.
  */
 /*
  * split out from pci.c
  * Copyright (c) 2010 Isaku Yamahata <yamahata at valinux co jp>
  *                    VA Linux Systems Japan K.K.
  */

 #include "hw/pci/pci_bridge.h"
 #include "hw/pci/pci_bus.h"
 #include "qemu/range.h"

 /* PCI bridge subsystem vendor ID helper functions */
 #define PCI_SSVID_SIZEOF        8
 #define PCI_SSVID_SVID          4
 #define PCI_SSVID_SSID          6

 int pci_bridge_ssvid_init(PCIDevice *dev, uint8_t offset,
                           uint16_t svid, uint16_t ssid)
 {
     int pos;
     pos = pci_add_capability(dev, PCI_CAP_ID_SSVID, offset, PCI_SSVID_SIZEOF);
     if (pos < 0) {
         return pos;
     }

     pci_set_word(dev->config + pos + PCI_SSVID_SVID, svid);
     pci_set_word(dev->config + pos + PCI_SSVID_SSID, ssid);
     return pos;
 }

 /* Accessor function to get parent bridge device from pci bus. */
 PCIDevice *pci_bridge_get_device(PCIBus *bus)
 {
     return bus->parent_dev;
 }

 /* Accessor function to get secondary bus from pci-to-pci bridge device */
 PCIBus *pci_bridge_get_sec_bus(PCIBridge *br)
 {
     return &br->sec_bus;
 }

 static uint32_t pci_config_get_io_base(const PCIDevice *d,
                                        uint32_t base, uint32_t base_upper16)
 {
     uint32_t val;

     val = ((uint32_t)d->config[base] & PCI_IO_RANGE_MASK) << 8;
     if (d->config[base] & PCI_IO_RANGE_TYPE_32) {
         val |= (uint32_t)pci_get_word(d->config + base_upper16) << 16;
     }
     return val;
 }

 static pcibus_t pci_config_get_memory_base(const PCIDevice *d, uint32_t base)
 {
     return ((pcibus_t)pci_get_word(d->config + base) & PCI_MEMORY_RANGE_MASK)
         << 16;
 }

 static pcibus_t pci_config_get_pref_base(const PCIDevice *d,
                                          uint32_t base, uint32_t upper)
 {
     pcibus_t tmp;
     pcibus_t val;

     tmp = (pcibus_t)pci_get_word(d->config + base);
     val = (tmp & PCI_PREF_RANGE_MASK) << 16;
     if (tmp & PCI_PREF_RANGE_TYPE_64) {
         val |= (pcibus_t)pci_get_long(d->config + upper) << 32;
     }
     return val;
 }

 /* accessor function to get bridge filtering base address */
 pcibus_t pci_bridge_get_base(const PCIDevice *bridge, uint8_t type)
 {
     pcibus_t base;
     if (type & PCI_BASE_ADDRESS_SPACE_IO) {
         base = pci_config_get_io_base(bridge,
                                       PCI_IO_BASE, PCI_IO_BASE_UPPER16);
     } else {
         if (type & PCI_BASE_ADDRESS_MEM_PREFETCH) {
             base = pci_config_get_pref_base(
                 bridge, PCI_PREF_MEMORY_BASE, PCI_PREF_BASE_UPPER32);
         } else {
             base = pci_config_get_memory_base(bridge, PCI_MEMORY_BASE);
         }
     }

     return base;
 }

 /* accessor funciton to get bridge filtering limit */
 pcibus_t pci_bridge_get_limit(const PCIDevice *bridge, uint8_t type)
 {
     pcibus_t limit;
     if (type & PCI_BASE_ADDRESS_SPACE_IO) {
         limit = pci_config_get_io_base(bridge,
                                       PCI_IO_LIMIT, PCI_IO_LIMIT_UPPER16);
         limit |= 0xfff;         /* PCI bridge spec 3.2.5.6. */
     } else {
         if (type & PCI_BASE_ADDRESS_MEM_PREFETCH) {
             limit = pci_config_get_pref_base(
                 bridge, PCI_PREF_MEMORY_LIMIT, PCI_PREF_LIMIT_UPPER32);
         } else {
             limit = pci_config_get_memory_base(bridge, PCI_MEMORY_LIMIT);
         }
         limit |= 0xfffff;       /* PCI bridge spec 3.2.5.{1, 8}. */
     }
     return limit;
 }

 static void pci_bridge_init_alias(PCIBridge *bridge, MemoryRegion *alias,
                                   uint8_t type, const char *name,
                                   MemoryRegion *space,
                                   MemoryRegion *parent_space,
                                   bool enabled)
 {
     PCIDevice *bridge_dev = PCI_DEVICE(bridge);
     pcibus_t base = pci_bridge_get_base(bridge_dev, type);
     pcibus_t limit = pci_bridge_get_limit(bridge_dev, type);
     /* TODO: this doesn't handle base = 0 limit = 2^64 - 1 correctly.
      * Apparently no way to do this with existing memory APIs. */
     pcibus_t size = enabled && limit >= base ? limit + 1 - base : 0;

     memory_region_init_alias(alias, OBJECT(bridge), name, space, base, size);
     memory_region_add_subregion_overlap(parent_space, base, alias, 1);
 }

 static void pci_bridge_init_vga_aliases(PCIBridge *br, PCIBus *parent,
                                         MemoryRegion *alias_vga)
 {
     PCIDevice *pd = PCI_DEVICE(br);
     uint16_t brctl = pci_get_word(pd->config + PCI_BRIDGE_CONTROL);

     memory_region_init_alias(&alias_vga[QEMU_PCI_VGA_IO_LO], OBJECT(br),
                              "pci_bridge_vga_io_lo", &br->address_space_io,
                              QEMU_PCI_VGA_IO_LO_BASE, QEMU_PCI_VGA_IO_LO_SIZE);
     memory_region_init_alias(&alias_vga[QEMU_PCI_VGA_IO_HI], OBJECT(br),
                              "pci_bridge_vga_io_hi", &br->address_space_io,
                              QEMU_PCI_VGA_IO_HI_BASE, QEMU_PCI_VGA_IO_HI_SIZE);
     memory_region_init_alias(&alias_vga[QEMU_PCI_VGA_MEM], OBJECT(br),
                              "pci_bridge_vga_mem", &br->address_space_mem,
                              QEMU_PCI_VGA_MEM_BASE, QEMU_PCI_VGA_MEM_SIZE);

     if (brctl & PCI_BRIDGE_CTL_VGA) {
         pci_register_vga(pd, &alias_vga[QEMU_PCI_VGA_MEM],
                          &alias_vga[QEMU_PCI_VGA_IO_LO],
                          &alias_vga[QEMU_PCI_VGA_IO_HI]);
     }
 }

 static PCIBridgeWindows *pci_bridge_region_init(PCIBridge *br)
 {
     PCIDevice *pd = PCI_DEVICE(br);
     PCIBus *parent = pd->bus;
     PCIBridgeWindows *w = g_new(PCIBridgeWindows, 1);
     uint16_t cmd = pci_get_word(pd->config + PCI_COMMAND);

     pci_bridge_init_alias(br, &w->alias_pref_mem,
                           PCI_BASE_ADDRESS_MEM_PREFETCH,
                           "pci_bridge_pref_mem",
                           &br->address_space_mem,
                           parent->address_space_mem,
                           cmd & PCI_COMMAND_MEMORY);
     pci_bridge_init_alias(br, &w->alias_mem,
                           PCI_BASE_ADDRESS_SPACE_MEMORY,
                           "pci_bridge_mem",
                           &br->address_space_mem,
                           parent->address_space_mem,
                           cmd & PCI_COMMAND_MEMORY);
     pci_bridge_init_alias(br, &w->alias_io,
                           PCI_BASE_ADDRESS_SPACE_IO,
                           "pci_bridge_io",
                           &br->address_space_io,
                           parent->address_space_io,
                           cmd & PCI_COMMAND_IO);

     pci_bridge_init_vga_aliases(br, parent, w->alias_vga);

     return w;
 }

 static void pci_bridge_region_del(PCIBridge *br, PCIBridgeWindows *w)
 {
     PCIDevice *pd = PCI_DEVICE(br);
     PCIBus *parent = pd->bus;

     memory_region_del_subregion(parent->address_space_io, &w->alias_io);
     memory_region_del_subregion(parent->address_space_mem, &w->alias_mem);
     memory_region_del_subregion(parent->address_space_mem, &w->alias_pref_mem);
     pci_unregister_vga(pd);
 }

 static void pci_bridge_region_cleanup(PCIBridge *br, PCIBridgeWindows *w)
 {
     memory_region_destroy(&w->alias_io);
     memory_region_destroy(&w->alias_mem);
     memory_region_destroy(&w->alias_pref_mem);
     memory_region_destroy(&w->alias_vga[QEMU_PCI_VGA_IO_LO]);
     memory_region_destroy(&w->alias_vga[QEMU_PCI_VGA_IO_HI]);
     memory_region_destroy(&w->alias_vga[QEMU_PCI_VGA_MEM]);
     g_free(w);
 }

 void pci_bridge_update_mappings(PCIBridge *br)
 {
     PCIBridgeWindows *w = br->windows;

     /* Make updates atomic to: handle the case of one VCPU updating the bridge
      * while another accesses an unaffected region. */
     memory_region_transaction_begin();
     pci_bridge_region_del(br, br->windows);
     br->windows = pci_bridge_region_init(br);
     memory_region_transaction_commit();
     pci_bridge_region_cleanup(br, w);
 }

 /* default write_config function for PCI-to-PCI bridge */
 void pci_bridge_write_config(PCIDevice *d,
                              uint32_t address, uint32_t val, int len)
 {
     PCIBridge *s = PCI_BRIDGE(d);
     uint16_t oldctl = pci_get_word(d->config + PCI_BRIDGE_CONTROL);
     uint16_t newctl;

     pci_default_write_config(d, address, val, len);

     if (ranges_overlap(address, len, PCI_COMMAND, 2) ||

         /* io base/limit */
         ranges_overlap(address, len, PCI_IO_BASE, 2) ||

         /* memory base/limit, prefetchable base/limit and
            io base/limit upper 16 */
         ranges_overlap(address, len, PCI_MEMORY_BASE, 20) ||

         /* vga enable */
         ranges_overlap(address, len, PCI_BRIDGE_CONTROL, 2)) {
         pci_bridge_update_mappings(s);
     }

     newctl = pci_get_word(d->config + PCI_BRIDGE_CONTROL);
     if (~oldctl & newctl & PCI_BRIDGE_CTL_BUS_RESET) {
         /* Trigger hot reset on 0->1 transition. */
         pci_bus_reset(&s->sec_bus);
     }
 }

 void pci_bridge_disable_base_limit(PCIDevice *dev)
 {
     uint8_t *conf = dev->config;

     pci_byte_test_and_set_mask(conf + PCI_IO_BASE,
                                PCI_IO_RANGE_MASK & 0xff);
     pci_byte_test_and_clear_mask(conf + PCI_IO_LIMIT,
                                  PCI_IO_RANGE_MASK & 0xff);
     pci_word_test_and_set_mask(conf + PCI_MEMORY_BASE,
                                PCI_MEMORY_RANGE_MASK & 0xffff);
     pci_word_test_and_clear_mask(conf + PCI_MEMORY_LIMIT,
                                  PCI_MEMORY_RANGE_MASK & 0xffff);
     pci_word_test_and_set_mask(conf + PCI_PREF_MEMORY_BASE,
                                PCI_PREF_RANGE_MASK & 0xffff);
     pci_word_test_and_clear_mask(conf + PCI_PREF_MEMORY_LIMIT,
                                  PCI_PREF_RANGE_MASK & 0xffff);
     pci_set_long(conf + PCI_PREF_BASE_UPPER32, 0);
     pci_set_long(conf + PCI_PREF_LIMIT_UPPER32, 0);
 }

 /* reset bridge specific configuration registers */
 void pci_bridge_reset(DeviceState *qdev)
 {
     PCIDevice *dev = PCI_DEVICE(qdev);
     uint8_t *conf = dev->config;

     conf[PCI_PRIMARY_BUS] = 0;
     conf[PCI_SECONDARY_BUS] = 0;
     conf[PCI_SUBORDINATE_BUS] = 0;
     conf[PCI_SEC_LATENCY_TIMER] = 0;

     /*
      * the default values for base/limit registers aren't specified
      * in the PCI-to-PCI-bridge spec. So we don't thouch them here.
      * Each implementation can override it.
      * typical implementation does
      * zero base/limit registers or
      * disable forwarding: pci_bridge_disable_base_limit()
      * If disable forwarding is wanted, call pci_bridge_disable_base_limit()
      * after this function.
      */
     pci_byte_test_and_clear_mask(conf + PCI_IO_BASE,
                                  PCI_IO_RANGE_MASK & 0xff);
     pci_byte_test_and_clear_mask(conf + PCI_IO_LIMIT,
                                  PCI_IO_RANGE_MASK & 0xff);
     pci_word_test_and_clear_mask(conf + PCI_MEMORY_BASE,
                                  PCI_MEMORY_RANGE_MASK & 0xffff);
     pci_word_test_and_clear_mask(conf + PCI_MEMORY_LIMIT,
                                  PCI_MEMORY_RANGE_MASK & 0xffff);
     pci_word_test_and_clear_mask(conf + PCI_PREF_MEMORY_BASE,
                                  PCI_PREF_RANGE_MASK & 0xffff);
     pci_word_test_and_clear_mask(conf + PCI_PREF_MEMORY_LIMIT,
                                  PCI_PREF_RANGE_MASK & 0xffff);
     pci_set_long(conf + PCI_PREF_BASE_UPPER32, 0);
     pci_set_long(conf + PCI_PREF_LIMIT_UPPER32, 0);

     pci_set_word(conf + PCI_BRIDGE_CONTROL, 0);
 }

 /* default qdev initialization function for PCI-to-PCI bridge */
 int pci_bridge_initfn(PCIDevice *dev, const char *typename)
 {
     PCIBus *parent = dev->bus;
     PCIBridge *br = PCI_BRIDGE(dev);
     PCIBus *sec_bus = &br->sec_bus;

     pci_word_test_and_set_mask(dev->config + PCI_STATUS,
                                PCI_STATUS_66MHZ | PCI_STATUS_FAST_BACK);

     /*
      * TODO: We implement VGA Enable in the Bridge Control Register
      * therefore per the PCI to PCI bridge spec we must also implement
      * VGA Palette Snooping.  When done, set this bit writable:
      *
      * pci_word_test_and_set_mask(dev->wmask + PCI_COMMAND,
      *                            PCI_COMMAND_VGA_PALETTE);
      */

     pci_config_set_class(dev->config, PCI_CLASS_BRIDGE_PCI);
     dev->config[PCI_HEADER_TYPE] =
         (dev->config[PCI_HEADER_TYPE] & PCI_HEADER_TYPE_MULTI_FUNCTION) |
         PCI_HEADER_TYPE_BRIDGE;
     pci_set_word(dev->config + PCI_SEC_STATUS,
                  PCI_STATUS_66MHZ | PCI_STATUS_FAST_BACK);

     /*
      * If we don't specify the name, the bus will be addressed as <id>.0, where
      * id is the device id.
      * Since PCI Bridge devices have a single bus each, we don't need the index:
      * let users address the bus using the device name.
      */
     if (!br->bus_name && dev->qdev.id && *dev->qdev.id) {
 	    br->bus_name = dev->qdev.id;
     }

     qbus_create_inplace(sec_bus, sizeof(br->sec_bus), typename, DEVICE(dev),
                         br->bus_name);
     sec_bus->parent_dev = dev;
     sec_bus->map_irq = br->map_irq ? br->map_irq : pci_swizzle_map_irq_fn;
     sec_bus->address_space_mem = &br->address_space_mem;
     memory_region_init(&br->address_space_mem, OBJECT(br), "pci_bridge_pci", UINT64_MAX);
     sec_bus->address_space_io = &br->address_space_io;
     memory_region_init(&br->address_space_io, OBJECT(br), "pci_bridge_io", 65536);
     br->windows = pci_bridge_region_init(br);
     QLIST_INIT(&sec_bus->child);
     QLIST_INSERT_HEAD(&parent->child, sec_bus, sibling);
     return 0;
 }

 /* default qdev clean up function for PCI-to-PCI bridge */
 void pci_bridge_exitfn(PCIDevice *pci_dev)
 {
     PCIBridge *s = PCI_BRIDGE(pci_dev);
     assert(QLIST_EMPTY(&s->sec_bus.child));
     QLIST_REMOVE(&s->sec_bus, sibling);
     pci_bridge_region_del(s, s->windows);
     pci_bridge_region_cleanup(s, s->windows);
     memory_region_destroy(&s->address_space_mem);
     memory_region_destroy(&s->address_space_io);
     /* object_unparent() is called automatically during device deletion */
 }

 /*
  * before qdev initialization(qdev_init()), this function sets bus_name and
  * map_irq callback which are necessry for pci_bridge_initfn() to
  * initialize bus.
  */
 void pci_bridge_map_irq(PCIBridge *br, const char* bus_name,
                         pci_map_irq_fn map_irq)
 {
     br->map_irq = map_irq;
     br->bus_name = bus_name;
 }

 static const TypeInfo pci_bridge_type_info = {
     .name = TYPE_PCI_BRIDGE,
     .parent = TYPE_PCI_DEVICE,
     .instance_size = sizeof(PCIBridge),
     .abstract = true,
 };

 static void pci_bridge_register_types(void)
 {
     type_register_static(&pci_bridge_type_info);
 }

 type_init(pci_bridge_register_types)
	/*
	* QEMU PCI bus manager
	*
	* Copyright (c) 2004 Fabrice Bellard
	*
	* Permission is hereby granted, free of charge, to any person obtaining a copy
	* of this software and associated documentation files (the "Software"), to dea

	* in the Software without restriction, including without limitation the rights
	* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
	* copies of the Software, and to permit persons to whom the Software is
	* furnished to do so, subject to the following conditions:
	*
	* The above copyright notice and this permission notice shall be included in
	* all copies or substantial portions of the Software.
	*
	* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
	* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
	* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
	* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
	* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM

	* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
	* THE SOFTWARE.
	*/
	/*
	* split out from pci.c
	* Copyright (c) 2010 Isaku Yamahata <yamahata at valinux co jp>
	* VA Linux Systems Japan K.K.
	*/

	#include "hw/pci/pci_bridge.h"
	#include "hw/pci/pci_bus.h"
	#include "qemu/range.h"

	/* PCI bridge subsystem vendor ID helper functions */
	#define PCI_SSVID_SIZEOF 8
	#define PCI_SSVID_SVID 4
	#define PCI_SSVID_SSID 6

	int pci_bridge_ssvid_init(PCIDevice *dev, uint8_t offset,
	uint16_t svid, uint16_t ssid)
	{
	int pos;
	pos = pci_add_capability(dev, PCI_CAP_ID_SSVID, offset, PCI_SSVID_SIZEOF);
	if (pos < 0) {
	return pos;
	}

	pci_set_word(dev->config + pos + PCI_SSVID_SVID, svid);
	pci_set_word(dev->config + pos + PCI_SSVID_SSID, ssid);
	return pos;
	}

	/* Accessor function to get parent bridge device from pci bus. */
	PCIDevice pci_bridge_get_device(PCIBus bus)
	{
	return bus->parent_dev;
	}

	/* Accessor function to get secondary bus from pci-to-pci bridge device */
	PCIBus pci_bridge_get_sec_bus(PCIBridge br)
	{
	return &br->sec_bus;
	}

	static uint32_t pci_config_get_io_base(const PCIDevice *d,
	uint32_t base, uint32_t base_upper16)
	{
	uint32_t val;

	val = ((uint32_t)d->config[base] & PCI_IO_RANGE_MASK) << 8;
	if (d->config[base] & PCI_IO_RANGE_TYPE_32) {
	val \|= (uint32_t)pci_get_word(d->config + base_upper16) << 16;
	}
	return val;
	}

	static pcibus_t pci_config_get_memory_base(const PCIDevice *d, uint32_t base)
	{
	return ((pcibus_t)pci_get_word(d->config + base) & PCI_MEMORY_RANGE_MASK)
	<< 16;
	}

	static pcibus_t pci_config_get_pref_base(const PCIDevice *d,
	uint32_t base, uint32_t upper)
	{
	pcibus_t tmp;
	pcibus_t val;

	tmp = (pcibus_t)pci_get_word(d->config + base);
	val = (tmp & PCI_PREF_RANGE_MASK) << 16;
	if (tmp & PCI_PREF_RANGE_TYPE_64) {
	val \|= (pcibus_t)pci_get_long(d->config + upper) << 32;
	}
	return val;
	}

	/* accessor function to get bridge filtering base address */
	pcibus_t pci_bridge_get_base(const PCIDevice *bridge, uint8_t type)
	{
	pcibus_t base;
	if (type & PCI_BASE_ADDRESS_SPACE_IO) {
	base = pci_config_get_io_base(bridge,
	PCI_IO_BASE, PCI_IO_BASE_UPPER16);
	} else {
	if (type & PCI_BASE_ADDRESS_MEM_PREFETCH) {
	base = pci_config_get_pref_base(
	bridge, PCI_PREF_MEMORY_BASE, PCI_PREF_BASE_UPPER32);
	} else {
	base = pci_config_get_memory_base(bridge, PCI_MEMORY_BASE);
	}
	}

	return base;
	}

	/* accessor funciton to get bridge filtering limit */
	pcibus_t pci_bridge_get_limit(const PCIDevice *bridge, uint8_t type)
	{
	pcibus_t limit;
	if (type & PCI_BASE_ADDRESS_SPACE_IO) {
	limit = pci_config_get_io_base(bridge,
	PCI_IO_LIMIT, PCI_IO_LIMIT_UPPER16);
	limit \|= 0xfff; /* PCI bridge spec 3.2.5.6. */
	} else {
	if (type & PCI_BASE_ADDRESS_MEM_PREFETCH) {
	limit = pci_config_get_pref_base(
	bridge, PCI_PREF_MEMORY_LIMIT, PCI_PREF_LIMIT_UPPER32);
	} else {
	limit = pci_config_get_memory_base(bridge, PCI_MEMORY_LIMIT);
	}
	limit \|= 0xfffff; /* PCI bridge spec 3.2.5.{1, 8}. */
	}
	return limit;
	}

	static void pci_bridge_init_alias(PCIBridge bridge, MemoryRegion alias,
	uint8_t type, const char *name,
	MemoryRegion *space,
	MemoryRegion *parent_space,
	bool enabled)
	{
	PCIDevice *bridge_dev = PCI_DEVICE(bridge);
	pcibus_t base = pci_bridge_get_base(bridge_dev, type);
	pcibus_t limit = pci_bridge_get_limit(bridge_dev, type);
	/* TODO: this doesn't handle base = 0 limit = 2^64 - 1 correctly.
	* Apparently no way to do this with existing memory APIs. */
	pcibus_t size = enabled && limit >= base ? limit + 1 - base : 0;

	memory_region_init_alias(alias, OBJECT(bridge), name, space, base, size);
	memory_region_add_subregion_overlap(parent_space, base, alias, 1);
	}

	static void pci_bridge_init_vga_aliases(PCIBridge br, PCIBus parent,
	MemoryRegion *alias_vga)
	{
	PCIDevice *pd = PCI_DEVICE(br);
	uint16_t brctl = pci_get_word(pd->config + PCI_BRIDGE_CONTROL);

	memory_region_init_alias(&alias_vga[QEMU_PCI_VGA_IO_LO], OBJECT(br),
	"pci_bridge_vga_io_lo", &br->address_space_io,
	QEMU_PCI_VGA_IO_LO_BASE, QEMU_PCI_VGA_IO_LO_SIZE);
	memory_region_init_alias(&alias_vga[QEMU_PCI_VGA_IO_HI], OBJECT(br),
	"pci_bridge_vga_io_hi", &br->address_space_io,
	QEMU_PCI_VGA_IO_HI_BASE, QEMU_PCI_VGA_IO_HI_SIZE);
	memory_region_init_alias(&alias_vga[QEMU_PCI_VGA_MEM], OBJECT(br),
	"pci_bridge_vga_mem", &br->address_space_mem,
	QEMU_PCI_VGA_MEM_BASE, QEMU_PCI_VGA_MEM_SIZE);

	if (brctl & PCI_BRIDGE_CTL_VGA) {
	pci_register_vga(pd, &alias_vga[QEMU_PCI_VGA_MEM],
	&alias_vga[QEMU_PCI_VGA_IO_LO],
	&alias_vga[QEMU_PCI_VGA_IO_HI]);
	}
	}

	static PCIBridgeWindows pci_bridge_region_init(PCIBridge br)
	{
	PCIDevice *pd = PCI_DEVICE(br);
	PCIBus *parent = pd->bus;
	PCIBridgeWindows *w = g_new(PCIBridgeWindows, 1);
	uint16_t cmd = pci_get_word(pd->config + PCI_COMMAND);

	pci_bridge_init_alias(br, &w->alias_pref_mem,
	PCI_BASE_ADDRESS_MEM_PREFETCH,
	"pci_bridge_pref_mem",
	&br->address_space_mem,
	parent->address_space_mem,
	cmd & PCI_COMMAND_MEMORY);
	pci_bridge_init_alias(br, &w->alias_mem,
	PCI_BASE_ADDRESS_SPACE_MEMORY,
	"pci_bridge_mem",
	&br->address_space_mem,
	parent->address_space_mem,
	cmd & PCI_COMMAND_MEMORY);
	pci_bridge_init_alias(br, &w->alias_io,
	PCI_BASE_ADDRESS_SPACE_IO,
	"pci_bridge_io",
	&br->address_space_io,
	parent->address_space_io,
	cmd & PCI_COMMAND_IO);

	pci_bridge_init_vga_aliases(br, parent, w->alias_vga);

	return w;
	}

	static void pci_bridge_region_del(PCIBridge br, PCIBridgeWindows w)
	{
	PCIDevice *pd = PCI_DEVICE(br);
	PCIBus *parent = pd->bus;

	memory_region_del_subregion(parent->address_space_io, &w->alias_io);
	memory_region_del_subregion(parent->address_space_mem, &w->alias_mem);
	memory_region_del_subregion(parent->address_space_mem, &w->alias_pref_mem);
	pci_unregister_vga(pd);
	}

	static void pci_bridge_region_cleanup(PCIBridge br, PCIBridgeWindows w)
	{
	memory_region_destroy(&w->alias_io);
	memory_region_destroy(&w->alias_mem);
	memory_region_destroy(&w->alias_pref_mem);
	memory_region_destroy(&w->alias_vga[QEMU_PCI_VGA_IO_LO]);
	memory_region_destroy(&w->alias_vga[QEMU_PCI_VGA_IO_HI]);
	memory_region_destroy(&w->alias_vga[QEMU_PCI_VGA_MEM]);
	g_free(w);
	}

	void pci_bridge_update_mappings(PCIBridge *br)
	{
	PCIBridgeWindows *w = br->windows;

	/* Make updates atomic to: handle the case of one VCPU updating the bridge
	* while another accesses an unaffected region. */
	memory_region_transaction_begin();
	pci_bridge_region_del(br, br->windows);
	br->windows = pci_bridge_region_init(br);
	memory_region_transaction_commit();
	pci_bridge_region_cleanup(br, w);
	}

	/* default write_config function for PCI-to-PCI bridge */
	void pci_bridge_write_config(PCIDevice *d,
	uint32_t address, uint32_t val, int len)
	{
	PCIBridge *s = PCI_BRIDGE(d);
	uint16_t oldctl = pci_get_word(d->config + PCI_BRIDGE_CONTROL);
	uint16_t newctl;

	pci_default_write_config(d, address, val, len);

	if (ranges_overlap(address, len, PCI_COMMAND, 2) \|\|

	/* io base/limit */
	ranges_overlap(address, len, PCI_IO_BASE, 2) \|\|

	/* memory base/limit, prefetchable base/limit and
	io base/limit upper 16 */
	ranges_overlap(address, len, PCI_MEMORY_BASE, 20) \|\|

	/* vga enable */
	ranges_overlap(address, len, PCI_BRIDGE_CONTROL, 2)) {
	pci_bridge_update_mappings(s);
	}

	newctl = pci_get_word(d->config + PCI_BRIDGE_CONTROL);
	if (~oldctl & newctl & PCI_BRIDGE_CTL_BUS_RESET) {
	/* Trigger hot reset on 0->1 transition. */
	pci_bus_reset(&s->sec_bus);
	}
	}

	void pci_bridge_disable_base_limit(PCIDevice *dev)
	{
	uint8_t *conf = dev->config;

	pci_byte_test_and_set_mask(conf + PCI_IO_BASE,
	PCI_IO_RANGE_MASK & 0xff);
	pci_byte_test_and_clear_mask(conf + PCI_IO_LIMIT,
	PCI_IO_RANGE_MASK & 0xff);
	pci_word_test_and_set_mask(conf + PCI_MEMORY_BASE,
	PCI_MEMORY_RANGE_MASK & 0xffff);
	pci_word_test_and_clear_mask(conf + PCI_MEMORY_LIMIT,
	PCI_MEMORY_RANGE_MASK & 0xffff);
	pci_word_test_and_set_mask(conf + PCI_PREF_MEMORY_BASE,
	PCI_PREF_RANGE_MASK & 0xffff);
	pci_word_test_and_clear_mask(conf + PCI_PREF_MEMORY_LIMIT,
	PCI_PREF_RANGE_MASK & 0xffff);
	pci_set_long(conf + PCI_PREF_BASE_UPPER32, 0);
	pci_set_long(conf + PCI_PREF_LIMIT_UPPER32, 0);
	}

	/* reset bridge specific configuration registers */
	void pci_bridge_reset(DeviceState *qdev)
	{
	PCIDevice *dev = PCI_DEVICE(qdev);
	uint8_t *conf = dev->config;

	conf[PCI_PRIMARY_BUS] = 0;
	conf[PCI_SECONDARY_BUS] = 0;
	conf[PCI_SUBORDINATE_BUS] = 0;
	conf[PCI_SEC_LATENCY_TIMER] = 0;

	/*
	* the default values for base/limit registers aren't specified
	* in the PCI-to-PCI-bridge spec. So we don't thouch them here.
	* Each implementation can override it.
	* typical implementation does
	* zero base/limit registers or
	* disable forwarding: pci_bridge_disable_base_limit()
	* If disable forwarding is wanted, call pci_bridge_disable_base_limit()
	* after this function.
	*/
	pci_byte_test_and_clear_mask(conf + PCI_IO_BASE,
	PCI_IO_RANGE_MASK & 0xff);
	pci_byte_test_and_clear_mask(conf + PCI_IO_LIMIT,
	PCI_IO_RANGE_MASK & 0xff);
	pci_word_test_and_clear_mask(conf + PCI_MEMORY_BASE,
	PCI_MEMORY_RANGE_MASK & 0xffff);
	pci_word_test_and_clear_mask(conf + PCI_MEMORY_LIMIT,
	PCI_MEMORY_RANGE_MASK & 0xffff);
	pci_word_test_and_clear_mask(conf + PCI_PREF_MEMORY_BASE,
	PCI_PREF_RANGE_MASK & 0xffff);
	pci_word_test_and_clear_mask(conf + PCI_PREF_MEMORY_LIMIT,
	PCI_PREF_RANGE_MASK & 0xffff);
	pci_set_long(conf + PCI_PREF_BASE_UPPER32, 0);
	pci_set_long(conf + PCI_PREF_LIMIT_UPPER32, 0);

	pci_set_word(conf + PCI_BRIDGE_CONTROL, 0);
	}

	/* default qdev initialization function for PCI-to-PCI bridge */
	int pci_bridge_initfn(PCIDevice dev, const char typename)
	{
	PCIBus *parent = dev->bus;
	PCIBridge *br = PCI_BRIDGE(dev);
	PCIBus *sec_bus = &br->sec_bus;

	pci_word_test_and_set_mask(dev->config + PCI_STATUS,
	PCI_STATUS_66MHZ \| PCI_STATUS_FAST_BACK);

	/*
	* TODO: We implement VGA Enable in the Bridge Control Register
	* therefore per the PCI to PCI bridge spec we must also implement
	* VGA Palette Snooping. When done, set this bit writable:
	*
	* pci_word_test_and_set_mask(dev->wmask + PCI_COMMAND,
	* PCI_COMMAND_VGA_PALETTE);
	*/

	pci_config_set_class(dev->config, PCI_CLASS_BRIDGE_PCI);
	dev->config[PCI_HEADER_TYPE] =
	(dev->config[PCI_HEADER_TYPE] & PCI_HEADER_TYPE_MULTI_FUNCTION) \|
	PCI_HEADER_TYPE_BRIDGE;
	pci_set_word(dev->config + PCI_SEC_STATUS,
	PCI_STATUS_66MHZ \| PCI_STATUS_FAST_BACK);

	/*
	* If we don't specify the name, the bus will be addressed as <id>.0, where
	* id is the device id.
	* Since PCI Bridge devices have a single bus each, we don't need the index:
	* let users address the bus using the device name.
	*/
	if (!br->bus_name && dev->qdev.id && *dev->qdev.id) {
	br->bus_name = dev->qdev.id;
	}

	qbus_create_inplace(sec_bus, sizeof(br->sec_bus), typename, DEVICE(dev),
	br->bus_name);
	sec_bus->parent_dev = dev;
	sec_bus->map_irq = br->map_irq ? br->map_irq : pci_swizzle_map_irq_fn;
	sec_bus->address_space_mem = &br->address_space_mem;
	memory_region_init(&br->address_space_mem, OBJECT(br), "pci_bridge_pci", UINT64_MAX);
	sec_bus->address_space_io = &br->address_space_io;
	memory_region_init(&br->address_space_io, OBJECT(br), "pci_bridge_io", 65536);
	br->windows = pci_bridge_region_init(br);
	QLIST_INIT(&sec_bus->child);
	QLIST_INSERT_HEAD(&parent->child, sec_bus, sibling);
	return 0;
	}

	/* default qdev clean up function for PCI-to-PCI bridge */
	void pci_bridge_exitfn(PCIDevice *pci_dev)
	{
	PCIBridge *s = PCI_BRIDGE(pci_dev);
	assert(QLIST_EMPTY(&s->sec_bus.child));
	QLIST_REMOVE(&s->sec_bus, sibling);
	pci_bridge_region_del(s, s->windows);
	pci_bridge_region_cleanup(s, s->windows);
	memory_region_destroy(&s->address_space_mem);
	memory_region_destroy(&s->address_space_io);
	/* object_unparent() is called automatically during device deletion */
	}

	/*
	* before qdev initialization(qdev_init()), this function sets bus_name and
	* map_irq callback which are necessry for pci_bridge_initfn() to
	* initialize bus.
	*/
	void pci_bridge_map_irq(PCIBridge br, const char bus_name,
	pci_map_irq_fn map_irq)
	{
	br->map_irq = map_irq;
	br->bus_name = bus_name;
	}

	static const TypeInfo pci_bridge_type_info = {
	.name = TYPE_PCI_BRIDGE,
	.parent = TYPE_PCI_DEVICE,
	.instance_size = sizeof(PCIBridge),
	.abstract = true,
	};

	static void pci_bridge_register_types(void)
	{
	type_register_static(&pci_bridge_type_info);
	}

	type_init(pci_bridge_register_types)