spapr_pci: spapr_iommu: Make DMA window a subregion

Currently the default DMA window is represented by a single MemoryRegion.
However there can be more than just one window so we need
a "root" memory region to be separated from the actual DMA window(s).

This introduces a "root" IOMMU memory region and adds a subregion for
the default DMA 32bit window. Following patches will add other
subregion(s).

This initializes a default DMA window subregion size to the guest RAM
size as this window can be switched into "bypass" mode which implements
direct DMA mapping.

Signed-off-by: Alexey Kardashevskiy <aik@ozlabs.ru>
Signed-off-by: Alexander Graf <agraf@suse.de>

hw/ppc/spapr_iommu.c

@@ -135,7 +135,7 @@ static int spapr_tce_table_realize(DeviceState *dev)
     trace_spapr_iommu_new_table(tcet->liobn, tcet, tcet->table, tcet->fd);
 
     memory_region_init_iommu(&tcet->iommu, OBJECT(dev), &spapr_iommu_ops,
-                             "iommu-spapr", UINT64_MAX);
+                             "iommu-spapr", ram_size);
 
     QLIST_INSERT_HEAD(&spapr_tce_tables, tcet, list);
 

hw/ppc/spapr_pci.c

@@ -610,6 +610,20 @@ static void spapr_phb_realize(DeviceState *dev, Error **errp)
                            PCI_DEVFN(0, 0), PCI_NUM_PINS, TYPE_PCI_BUS);
     phb->bus = bus;
 
+    /*
+     * Initialize PHB address space.
+     * By default there will be at least one subregion for default
+     * 32bit DMA window.
+     * Later the guest might want to create another DMA window
+     * which will become another memory subregion.
+     */
+    sprintf(namebuf, "%s.iommu-root", sphb->dtbusname);
+
+    memory_region_init(&sphb->iommu_root, OBJECT(sphb),
+                       namebuf, UINT64_MAX);
+    address_space_init(&sphb->iommu_as, &sphb->iommu_root,
+                       sphb->dtbusname);
+
     pci_setup_iommu(bus, spapr_pci_dma_iommu, sphb);
 
     pci_bus_set_route_irq_fn(bus, spapr_route_intx_pin_to_irq);
@@ -648,8 +662,10 @@ static void spapr_phb_finish_realize(sPAPRPHBState *sphb, Error **errp)
                    sphb->dtbusname);
         return ;
     }
-    address_space_init(&sphb->iommu_as, spapr_tce_get_iommu(sphb->tcet),
-                       sphb->dtbusname);
+
+    /* Register default 32bit DMA window */
+    memory_region_add_subregion(&sphb->iommu_root, 0,
+                                spapr_tce_get_iommu(sphb->tcet));
 }
 
 static void spapr_phb_reset(DeviceState *qdev)

include/hw/pci-host/spapr.h

@@ -64,6 +64,7 @@ struct sPAPRPHBState {
     uint64_t dma_window_size;
     sPAPRTCETable *tcet;
     AddressSpace iommu_as;
+    MemoryRegion iommu_root;
 
     struct spapr_pci_lsi {
         uint32_t irq;