[Qemu-devel] [PATCH V6 for-2.3 14/26] hw/pci-host/piix: implement TYPE_PCI_HOST_BRIDGE_SNOOPED interface

[Marcel Apfelbaum <marcel@redhat.com>]

The PIIX holds a list of snooping host bridges that is populated
by a registration function that shall be used by any host bridge
that needs to use PIIX configuration space to complete their
configuration cycles.

PIIX monitors acceses to configuration registers and passes them
to the corresponding host bridge if the input bus number is
in its bus range.

Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
---
 hw/pci-host/piix.c        | 118 +++++++++++++++++++++++++++++++++++++++++++++-
 hw/pci/pci_host.c         |  28 +++++++++++
 include/hw/i386/pc.h      |   6 +++
 include/hw/pci/pci_host.h |   3 ++
 4 files changed, 154 insertions(+), 1 deletion(-)

diff --git a/hw/pci-host/piix.c b/hw/pci-host/piix.c
index 0033ab4..f512765 100644
--- a/hw/pci-host/piix.c
+++ b/hw/pci-host/piix.c
@@ -50,6 +50,12 @@ typedef struct I440FXState {
     PcPciInfo pci_info;
     uint64_t pci_hole64_size;
     uint32_t short_root_bus;
+
+    /*
+     * List of PCI host bridges listening to
+     * the same configuration registers.
+     */
+    GPtrArray *snooping_hosts;
 } I440FXState;
 
 #define PIIX_NUM_PIC_IRQS       16      /* i8259 * 2 */
@@ -255,14 +261,80 @@ static void i440fx_pcihost_get_pci_hole64_end(Object *obj, Visitor *v,
     visit_type_uint64(v, &w64.end, name, errp);
 }
 
+static PCIBus *i440fx_find_target_bus(I440FXState *i440fx, uint8_t bus_num)
+{
+    PCIHostState *host = PCI_HOST_BRIDGE(i440fx);
+    PCIBus *target_bus = NULL;
+
+    if (bus_num == pci_bus_num(host->bus)) {
+        target_bus = host->bus;
+    } else {
+        int i;
+
+        for (i = 0; i < i440fx->snooping_hosts->len; i++) {
+            PCIHostState *s_host = g_ptr_array_index(i440fx->snooping_hosts, i);
+            Range r = pci_host_get_buses_range(s_host);
+
+            if (r.begin <= bus_num && r.end >= bus_num) {
+                target_bus = s_host->bus;
+            }
+
+        }
+    }
+
+    return target_bus;
+}
+
+static void i440fx_pcihost_data_write(void *opaque, hwaddr addr,
+                                      uint64_t val, unsigned len)
+{
+    uint32_t config_reg = PCI_HOST_BRIDGE(opaque)->config_reg;
+
+    if (config_reg & (1u << 31)) {
+        uint8_t bus_num = (config_reg >> 16) & 0xFF;
+        I440FXState *i440fx = I440FX_PCI_HOST_BRIDGE(opaque);
+        PCIBus *target_bus = i440fx_find_target_bus(i440fx, bus_num);
+
+        if (target_bus) {
+            pci_data_write(target_bus, config_reg | (addr & 3), val, len);
+        }
+    }
+}
+
+static uint64_t i440fx_pcihost_data_read(void *opaque,
+                                         hwaddr addr, unsigned len)
+{
+    uint32_t config_reg = PCI_HOST_BRIDGE(opaque)->config_reg;
+
+    if (config_reg & (1U << 31)) {
+        int bus_num = (config_reg >> 16) & 0xFF;
+        I440FXState *i440fx = I440FX_PCI_HOST_BRIDGE(opaque);
+        PCIBus *target_bus = i440fx_find_target_bus(i440fx, bus_num);
+
+        if (target_bus) {
+            return pci_data_read(target_bus, config_reg | (addr & 3), len);
+        }
+    }
+
+    return 0xffffffff;
+}
+
+const MemoryRegionOps i440fx_pcihost_data_le_ops = {
+    .read = i440fx_pcihost_data_read,
+    .write = i440fx_pcihost_data_write,
+    .endianness = DEVICE_LITTLE_ENDIAN,
+};
+
 static void i440fx_pcihost_initfn(Object *obj)
 {
     PCIHostState *s = PCI_HOST_BRIDGE(obj);
     I440FXState *d = I440FX_PCI_HOST_BRIDGE(obj);
 
+    d->snooping_hosts = g_ptr_array_new();
+
     memory_region_init_io(&s->conf_mem, obj, &pci_host_conf_le_ops, s,
                           "pci-conf-idx", 4);
-    memory_region_init_io(&s->data_mem, obj, &pci_host_data_le_ops, s,
+    memory_region_init_io(&s->data_mem, obj, &i440fx_pcihost_data_le_ops, s,
                           "pci-conf-data", 4);
 
     object_property_add(obj, PCI_HOST_PROP_PCI_HOLE_START, "int",
@@ -400,6 +472,40 @@ PCIBus *find_i440fx(void)
     return s ? s->bus : NULL;
 }
 
+/*
+ * Returns 0 on successs, -1 if i440fx host was not
+ * found or the bus number is already in use.
+ */
+int i440fx_register_snooping_host(PCIHostState *host)
+{
+    I440FXState *s = OBJECT_CHECK(I440FXState,
+                                  object_resolve_path("/machine/i440fx", NULL),
+                                  TYPE_I440FX_PCI_HOST_BRIDGE);
+    uint8_t bus_num = pci_bus_num(host->bus);
+    int i;
+
+    /* i440fx host not found */
+    if (!s) {
+        return -1;
+    }
+
+    /* 0 is reserved for i440fx host bridge */
+    if (bus_num == 0) {
+        return -1;
+    }
+
+    /* check if the bus number is unique */
+    for (i = 0; i < s->snooping_hosts->len; i++) {
+        PCIHostState *s_host = g_ptr_array_index(s->snooping_hosts, i);
+        if (bus_num == pci_bus_num(s_host->bus)) {
+            return -1;
+        }
+    }
+
+    g_ptr_array_add(s->snooping_hosts, host);
+    return 0;
+}
+
 /* PIIX3 PCI to ISA bridge */
 static void piix3_set_irq_pic(PIIX3State *piix3, int pic_irq)
 {
@@ -742,6 +848,13 @@ static const char *i440fx_pcihost_root_bus_path(PCIHostState *host_bridge,
     return "0000:00";
 }
 
+static GPtrArray *i440fx_snooping_hosts(PCIHostState *host_bridge)
+{
+    I440FXState *s = I440FX_PCI_HOST_BRIDGE(host_bridge);
+
+    return s->snooping_hosts;
+}
+
 static Property i440fx_props[] = {
     DEFINE_PROP_SIZE(PCI_HOST_PROP_PCI_HOLE64_SIZE, I440FXState,
                      pci_hole64_size, DEFAULT_PCI_HOLE64_SIZE),
@@ -753,11 +866,13 @@ static void i440fx_pcihost_class_init(ObjectClass *klass, void *data)
 {
     DeviceClass *dc = DEVICE_CLASS(klass);
     PCIHostBridgeClass *hc = PCI_HOST_BRIDGE_CLASS(klass);
+    PCIHostBridgeSnoopedClass *sc = TYPE_PCI_HOST_BRIDGE_SNOOPED_CLASS(klass);
 
     hc->root_bus_path = i440fx_pcihost_root_bus_path;
     dc->realize = i440fx_pcihost_realize;
     dc->fw_name = "pci";
     dc->props = i440fx_props;
+    sc->snooping_hosts = i440fx_snooping_hosts;
 }
 
 static const TypeInfo i440fx_pcihost_info = {
@@ -768,6 +883,7 @@ static const TypeInfo i440fx_pcihost_info = {
     .class_init    = i440fx_pcihost_class_init,
     .interfaces    = (InterfaceInfo[]) {
         { TYPE_PCI_MAIN_HOST_BRIDGE },
+        { TYPE_PCI_HOST_BRIDGE_SNOOPED },
         { }
     }
 
diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c
index 288e74c..35e462b 100644
--- a/hw/pci/pci_host.c
+++ b/hw/pci/pci_host.c
@@ -20,6 +20,8 @@
 
 #include "hw/pci/pci.h"
 #include "hw/pci/pci_host.h"
+#include "hw/pci/pci_bus.h"
+#include "qemu/range.h"
 #include "trace.h"
 
 /* debug PCI */
@@ -32,6 +34,32 @@ do { printf("pci_host_data: " fmt , ## __VA_ARGS__); } while (0)
 #define PCI_DPRINTF(fmt, ...)
 #endif
 
+Range pci_host_get_buses_range(PCIHostState *host)
+{
+    uint8_t root_bus_num = pci_bus_num(host->bus);
+    Range r = {root_bus_num, root_bus_num};
+    int i;
+
+    for (i = 0; i < ARRAY_SIZE(host->bus->devices); ++i) {
+        PCIDevice *dev = host->bus->devices[i];
+        PCIDeviceClass *pc;
+
+        if (!dev) {
+            continue;
+        }
+
+        pc = PCI_DEVICE_GET_CLASS(dev);
+
+        if (pc->is_bridge) {
+            uint8_t subordinate = dev->config[PCI_SUBORDINATE_BUS];
+            if (subordinate > r.end) {
+                r.end = subordinate;
+            }
+        }
+    }
+
+    return r;
+}
 /*
  * PCI address
  * bit 16 - 24: bus number
diff --git a/include/hw/i386/pc.h b/include/hw/i386/pc.h
index 1b35168..a918a61 100644
--- a/include/hw/i386/pc.h
+++ b/include/hw/i386/pc.h
@@ -241,6 +241,12 @@ PCIBus *i440fx_init(PCII440FXState **pi440fx_state, int *piix_devfn,
                     MemoryRegion *ram_memory);
 
 PCIBus *find_i440fx(void);
+/*
+ * Register hosts without their own configuration registers
+ * to i440fx main PCI host bridge
+ */
+int i440fx_register_snooping_host(PCIHostState *host);
+
 /* piix4.c */
 extern PCIDevice *piix4_dev;
 int piix4_init(PCIBus *bus, ISABus **isa_bus, int devfn);
diff --git a/include/hw/pci/pci_host.h b/include/hw/pci/pci_host.h
index a041919..dc7ccb2 100644
--- a/include/hw/pci/pci_host.h
+++ b/include/hw/pci/pci_host.h
@@ -87,6 +87,9 @@ typedef struct PCIHostBridgeSnoopedClass {
     GPtrArray *(*snooping_hosts)(PCIHostState *);
 } PCIHostBridgeSnoopedClass;
 
+/* Returns the buses interval owned by the input host */
+Range pci_host_get_buses_range(PCIHostState *host);
+
 /* common internal helpers for PCI/PCIe hosts, cut off overflows */
 void pci_host_config_write_common(PCIDevice *pci_dev, uint32_t addr,
                                   uint32_t limit, uint32_t val, uint32_t len);
-- 
2.1.0