diff --git a/hw/pci.c b/hw/pci.c
index 2dc1577..afcb33c 100644
--- a/hw/pci.c
+++ b/hw/pci.c
@@ -158,6 +158,19 @@ static void pci_device_reset(PCIDevice *dev)
     pci_update_mappings(dev);
 }
 
+static int pci_no_translate(PCIDevice *iommu,
+                            PCIDevice *dev,
+                            pcibus_t addr,
+                            target_phys_addr_t *paddr,
+                            target_phys_addr_t *len,
+                            unsigned perms)
+{
+    *paddr = addr;
+    *len = -1;
+
+    return 0;
+}
+
 static void pci_bus_reset(void *opaque)
 {
     PCIBus *bus = opaque;
@@ -220,7 +233,10 @@ void pci_bus_new_inplace(PCIBus *bus, DeviceState *parent,
 {
     qbus_create_inplace(&bus->qbus, &pci_bus_info, parent, name);
     assert(PCI_FUNC(devfn_min) == 0);
-    bus->devfn_min = devfn_min;
+
+    bus->devfn_min  = devfn_min;
+    bus->iommu      = NULL;
+    bus->translate  = pci_no_translate;
 
     /* host bridge */
     QLIST_INIT(&bus->child);
@@ -1789,3 +1805,176 @@ static char *pcibus_get_dev_path(DeviceState *dev)
     return strdup(path);
 }
 
+void pci_register_iommu(PCIDevice *iommu,
+                        PCITranslateFunc *translate)
+{
+    iommu->bus->iommu = iommu;
+    iommu->bus->translate = translate;
+}
+
+void pci_memory_rw(PCIDevice *dev,
+                   pcibus_t addr,
+                   uint8_t *buf,
+                   pcibus_t len,
+                   int is_write)
+{
+    int err;
+    unsigned perms;
+    PCIDevice *iommu = dev->bus->iommu;
+    target_phys_addr_t paddr, plen;
+
+    perms = is_write ? IOMMU_PERM_WRITE : IOMMU_PERM_READ;
+
+    while (len) {
+        err = dev->bus->translate(iommu, dev, addr, &paddr, &plen, perms);
+        if (err) {
+            return;
+        }
+
+        /* The translation might be valid for larger regions. */
+        if (plen > len) {
+            plen = len;
+        }
+
+        cpu_physical_memory_rw(paddr, buf, plen, is_write);
+
+        len -= plen;
+        addr += plen;
+        buf += plen;
+    }
+}
+
+static void pci_memory_register_map(PCIDevice *dev,
+                                    pcibus_t addr,
+                                    pcibus_t len,
+                                    target_phys_addr_t paddr,
+                                    PCIInvalidateMapFunc *invalidate,
+                                    void *invalidate_opaque)
+{
+    PCIMemoryMap *map;
+
+    map = qemu_malloc(sizeof(PCIMemoryMap));
+    map->addr               = addr;
+    map->len                = len;
+    map->paddr              = paddr;
+    map->invalidate         = invalidate;
+    map->invalidate_opaque  = invalidate_opaque;
+
+    QLIST_INSERT_HEAD(&dev->memory_maps, map, list);
+}
+
+static void pci_memory_unregister_map(PCIDevice *dev,
+                                      target_phys_addr_t paddr,
+                                      target_phys_addr_t len)
+{
+    PCIMemoryMap *map;
+
+    QLIST_FOREACH(map, &dev->memory_maps, list) {
+        if (map->paddr == paddr && map->len == len) {
+            QLIST_REMOVE(map, list);
+            free(map);
+        }
+    }
+}
+
+void pci_memory_invalidate_range(PCIDevice *dev,
+                                 pcibus_t addr,
+                                 pcibus_t len)
+{
+    PCIMemoryMap *map;
+
+    QLIST_FOREACH(map, &dev->memory_maps, list) {
+        if (ranges_overlap(addr, len, map->addr, map->len)) {
+            map->invalidate(map->invalidate_opaque);
+            QLIST_REMOVE(map, list);
+            free(map);
+        }
+    }
+}
+
+void *pci_memory_map(PCIDevice *dev,
+                     PCIInvalidateMapFunc *cb,
+                     void *opaque,
+                     pcibus_t addr,
+                     target_phys_addr_t *len,
+                     int is_write)
+{
+    int err;
+    unsigned perms;
+    PCIDevice *iommu = dev->bus->iommu;
+    target_phys_addr_t paddr, plen;
+
+    perms = is_write ? IOMMU_PERM_WRITE : IOMMU_PERM_READ;
+
+    plen = *len;
+    err = dev->bus->translate(iommu, dev, addr, &paddr, &plen, perms);
+    if (err) {
+        return NULL;
+    }
+
+    /*
+     * If this is true, the virtual region is contiguous,
+     * but the translated physical region isn't. We just
+     * clamp *len, much like cpu_physical_memory_map() does.
+     */
+    if (plen < *len) {
+        *len = plen;
+    }
+
+    /* We treat maps as remote TLBs to cope with stuff like AIO. */
+    if (cb) {
+        pci_memory_register_map(dev, addr, *len, paddr, cb, opaque);
+    }
+
+    return cpu_physical_memory_map(paddr, len, is_write);
+}
+
+void pci_memory_unmap(PCIDevice *dev,
+                      void *buffer,
+                      target_phys_addr_t len,
+                      int is_write,
+                      target_phys_addr_t access_len)
+{
+    cpu_physical_memory_unmap(buffer, len, is_write, access_len);
+    pci_memory_unregister_map(dev, (target_phys_addr_t) buffer, len);
+}
+
+#define DEFINE_PCI_LD(suffix, size)                                       \
+uint##size##_t pci_ld##suffix(PCIDevice *dev, pcibus_t addr)              \
+{                                                                         \
+    int err;                                                              \
+    target_phys_addr_t paddr, plen;                                       \
+                                                                          \
+    err = dev->bus->translate(dev->bus->iommu, dev,                       \
+                              addr, &paddr, &plen, IOMMU_PERM_READ);      \
+    if (err || (plen < size / 8)) {                                       \
+        return 0;                                                         \
+    }                                                                     \
+                                                                          \
+    return ld##suffix##_phys(paddr);                                      \
+}
+
+#define DEFINE_PCI_ST(suffix, size)                                       \
+void pci_st##suffix(PCIDevice *dev, pcibus_t addr, uint##size##_t val)    \
+{                                                                         \
+    int err;                                                              \
+    target_phys_addr_t paddr, plen;                                       \
+                                                                          \
+    err = dev->bus->translate(dev->bus->iommu, dev,                       \
+                              addr, &paddr, &plen, IOMMU_PERM_WRITE);     \
+    if (err || (plen < size / 8)) {                                       \
+        return;                                                           \
+    }                                                                     \
+                                                                          \
+    st##suffix##_phys(paddr, val);                                        \
+}
+
+DEFINE_PCI_LD(ub, 8)
+DEFINE_PCI_LD(uw, 16)
+DEFINE_PCI_LD(l, 32)
+DEFINE_PCI_LD(q, 64)
+
+DEFINE_PCI_ST(b, 8)
+DEFINE_PCI_ST(w, 16)
+DEFINE_PCI_ST(l, 32)
+DEFINE_PCI_ST(q, 64)
diff --git a/hw/pci.h b/hw/pci.h
index c551f96..c95863a 100644
--- a/hw/pci.h
+++ b/hw/pci.h
@@ -172,6 +172,8 @@ struct PCIDevice {
     char *romfile;
     ram_addr_t rom_offset;
     uint32_t rom_bar;
+
+    QLIST_HEAD(, PCIMemoryMap) memory_maps;
 };
 
 PCIDevice *pci_register_device(PCIBus *bus, const char *name,
@@ -391,4 +393,71 @@ static inline int ranges_overlap(uint64_t first1, uint64_t len1,
     return !(last2 < first1 || last1 < first2);
 }
 
+/*
+ * Memory I/O and PCI IOMMU definitions.
+ */
+
+#define IOMMU_PERM_READ     (1 << 0)
+#define IOMMU_PERM_WRITE    (1 << 1)
+#define IOMMU_PERM_RW       (IOMMU_PERM_READ | IOMMU_PERM_WRITE)
+
+typedef int PCIInvalidateMapFunc(void *opaque);
+typedef int PCITranslateFunc(PCIDevice *iommu,
+                             PCIDevice *dev,
+                             pcibus_t addr,
+                             target_phys_addr_t *paddr,
+                             target_phys_addr_t *len,
+                             unsigned perms);
+
+void pci_memory_rw(PCIDevice *dev,
+                   pcibus_t addr,
+                   uint8_t *buf,
+                   pcibus_t len,
+                   int is_write);
+void *pci_memory_map(PCIDevice *dev,
+                     PCIInvalidateMapFunc *cb,
+                     void *opaque,
+                     pcibus_t addr,
+                     target_phys_addr_t *len,
+                     int is_write);
+void pci_memory_unmap(PCIDevice *dev,
+                      void *buffer,
+                      target_phys_addr_t len,
+                      int is_write,
+                      target_phys_addr_t access_len);
+void pci_register_iommu(PCIDevice *dev, PCITranslateFunc *translate);
+void pci_memory_invalidate_range(PCIDevice *dev, pcibus_t addr, pcibus_t len);
+
+#define DECLARE_PCI_LD(suffix, size)                                    \
+uint##size##_t pci_ld##suffix(PCIDevice *dev, pcibus_t addr);
+
+#define DECLARE_PCI_ST(suffix, size)                                    \
+void pci_st##suffix(PCIDevice *dev, pcibus_t addr, uint##size##_t val);
+
+DECLARE_PCI_LD(ub, 8)
+DECLARE_PCI_LD(uw, 16)
+DECLARE_PCI_LD(l, 32)
+DECLARE_PCI_LD(q, 64)
+
+DECLARE_PCI_ST(b, 8)
+DECLARE_PCI_ST(w, 16)
+DECLARE_PCI_ST(l, 32)
+DECLARE_PCI_ST(q, 64)
+
+static inline void pci_memory_read(PCIDevice *dev,
+                                   pcibus_t addr,
+                                   uint8_t *buf,
+                                   pcibus_t len)
+{
+    pci_memory_rw(dev, addr, buf, len, 0);
+}
+
+static inline void pci_memory_write(PCIDevice *dev,
+                                    pcibus_t addr,
+                                    const uint8_t *buf,
+                                    pcibus_t len)
+{
+    pci_memory_rw(dev, addr, (uint8_t *) buf, len, 1);
+}
+
 #endif
diff --git a/hw/pci_internals.h b/hw/pci_internals.h
index e3c93a3..fb134b9 100644
--- a/hw/pci_internals.h
+++ b/hw/pci_internals.h
@@ -33,6 +33,9 @@ struct PCIBus {
        Keep a count of the number of devices with raised IRQs.  */
     int nirq;
     int *irq_count;
+
+    PCIDevice                       *iommu;
+    PCITranslateFunc                *translate;
 };
 
 struct PCIBridge {
@@ -44,4 +47,13 @@ struct PCIBridge {
     const char *bus_name;
 };
 
+struct PCIMemoryMap {
+    pcibus_t                        addr;
+    pcibus_t                        len;
+    target_phys_addr_t              paddr;
+    PCIInvalidateMapFunc            *invalidate;
+    void                            *invalidate_opaque;
+    QLIST_ENTRY(PCIMemoryMap)       list;
+};
+
 #endif /* QEMU_PCI_INTERNALS_H */
diff --git a/qemu-common.h b/qemu-common.h
index d735235..8b060e8 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -218,6 +218,7 @@ typedef struct SMBusDevice SMBusDevice;
 typedef struct PCIHostState PCIHostState;
 typedef struct PCIExpressHost PCIExpressHost;
 typedef struct PCIBus PCIBus;
+typedef struct PCIMemoryMap PCIMemoryMap;
 typedef struct PCIDevice PCIDevice;
 typedef struct PCIBridge PCIBridge;
 typedef struct SerialState SerialState;
