[Qemu-ppc] [PATCH|RFC 1/1] pci: allow 0 address for PCI IO/MEM regions

[Laurent Vivier]

From: Michael Roth <address@hidden>

Some kernels program a 0 address for io regions. PCI 3.0 spec
section 6.2.5.1 doesn't seem to disallow this.

Signed-off-by: Michael Roth <address@hidden>
[lvivier: add accept_addr_0 in PCIBus to conditionally allow addr 0,
 as this can break other architectures]
Signed-off-by: Laurent Vivier <address@hidden>
---
 hw/pci/pci.c             | 9 ++++++---
 hw/ppc/spapr_pci.c       | 1 +
 include/hw/pci/pci_bus.h | 5 +++++
 3 files changed, 12 insertions(+), 3 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index a017614..b5a3658 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -338,6 +338,7 @@ static void pci_bus_init(PCIBus *bus, DeviceState *parent,
     bus->devfn_min = devfn_min;
     bus->address_space_mem = address_space_mem;
     bus->address_space_io = address_space_io;
+    bus->accept_addr_0 = false;
 
     /* host bridge */
     QLIST_INIT(&bus->child);
@@ -1065,6 +1066,7 @@ static pcibus_t pci_bar_address(PCIDevice *d,
     pcibus_t new_addr, last_addr;
     int bar = pci_bar(d, reg);
     uint16_t cmd = pci_get_word(d->config + PCI_COMMAND);
+    bool accept_addr_0 = d->bus->accept_addr_0;
 
     if (type & PCI_BASE_ADDRESS_SPACE_IO) {
         if (!(cmd & PCI_COMMAND_IO)) {
@@ -1075,7 +1077,8 @@ static pcibus_t pci_bar_address(PCIDevice *d,
         /* Check if 32 bit BAR wraps around explicitly.
          * TODO: make priorities correct and remove this work around.
          */
-        if (last_addr <= new_addr || new_addr == 0 || last_addr >= UINT32_MAX) 
{
+        if (last_addr <= new_addr || last_addr >= UINT32_MAX ||
+            (!accept_addr_0 && new_addr == 0)) {
             return PCI_BAR_UNMAPPED;
         }
         return new_addr;
@@ -1099,8 +1102,8 @@ static pcibus_t pci_bar_address(PCIDevice *d,
     /* XXX: as we cannot support really dynamic
        mappings, we handle specific values as invalid
        mappings. */
-    if (last_addr <= new_addr || new_addr == 0 ||
-        last_addr == PCI_BAR_UNMAPPED) {
+    if (last_addr <= new_addr || last_addr == PCI_BAR_UNMAPPED ||
+        (!accept_addr_0 && new_addr == 0)) {
         return PCI_BAR_UNMAPPED;
     }
 
diff --git a/hw/ppc/spapr_pci.c b/hw/ppc/spapr_pci.c
index a8f79d8..29374ea 100644
--- a/hw/ppc/spapr_pci.c
+++ b/hw/ppc/spapr_pci.c
@@ -1302,6 +1302,7 @@ static void spapr_phb_realize(DeviceState *dev, Error 
**errp)
                            pci_spapr_set_irq, pci_spapr_map_irq, sphb,
                            &sphb->memspace, &sphb->iospace,
                            PCI_DEVFN(0, 0), PCI_NUM_PINS, TYPE_PCI_BUS);
+    bus->accept_addr_0 = true;
     phb->bus = bus;
     qbus_set_hotplug_handler(BUS(phb->bus), DEVICE(sphb), NULL);
 
diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h
index 403fec6..7eeeaa9 100644
--- a/include/hw/pci/pci_bus.h
+++ b/include/hw/pci/pci_bus.h
@@ -39,6 +39,11 @@ struct PCIBus {
        Keep a count of the number of devices with raised IRQs.  */
     int nirq;
     int *irq_count;
+    /* XXX: pseries kernels can configure BARs at address 0
+     * it is allowed by specs but not managed correctly
+     * by other architectures...
+     */
+    bool accept_addr_0;
 };
 
 typedef struct PCIBridgeWindows PCIBridgeWindows;
-- 
2.1.0