[Qemu-devel] [PATCH v2] pci: allow 0 address for PCI IO/MEM regions

[Laurent Vivier <lvivier@redhat.com>]

From: Michael Roth <mdroth@linux.vnet.ibm.com>

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 <mdroth@linux.vnet.ibm.com>
[lvivier: add pci_allow_0_addr in MachineClass to conditionally
allow addr 0 for pseries, as this can break other architectures]
Signed-off-by: Laurent Vivier <lvivier@redhat.com>
---
v2: move flag from PCIBus to MachineClass, rename it pci_allow_0_address
 hw/pci/pci.c        | 12 +++++++++---
 hw/ppc/spapr.c      |  1 +
 include/hw/boards.h |  3 ++-
 3 files changed, 12 insertions(+), 4 deletions(-)

diff --git a/hw/pci/pci.c b/hw/pci/pci.c
index a017614..9f57aea 100644
--- a/hw/pci/pci.c
+++ b/hw/pci/pci.c
@@ -38,6 +38,7 @@
 #include "hw/pci/msix.h"
 #include "exec/address-spaces.h"
 #include "hw/hotplug.h"
+#include "hw/boards.h"
 
 //#define DEBUG_PCI
 #ifdef DEBUG_PCI
@@ -1065,6 +1066,10 @@ 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);
+    Object *machine = qdev_get_machine();
+    ObjectClass *oc = object_get_class(machine);
+    MachineClass *mc = MACHINE_CLASS(oc);
+    bool allow_0_address = mc->pci_allow_0_address;
 
     if (type & PCI_BASE_ADDRESS_SPACE_IO) {
         if (!(cmd & PCI_COMMAND_IO)) {
@@ -1075,7 +1080,8 @@ 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 ||
+            (!allow_0_address && new_addr == 0)) {
             return PCI_BAR_UNMAPPED;
         }
         return new_addr;
@@ -1099,8 +1105,8 @@ 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 ||
+        (!allow_0_address && new_addr == 0)) {
         return PCI_BAR_UNMAPPED;
     }
 
diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
index a6f1947..bf0c64f 100644
--- a/hw/ppc/spapr.c
+++ b/hw/ppc/spapr.c
@@ -1835,6 +1835,7 @@ static void spapr_machine_class_init(ObjectClass *oc, void *data)
     mc->default_ram_size = 512 * M_BYTE;
     mc->kvm_type = spapr_kvm_type;
     mc->has_dynamic_sysbus = true;
+    mc->pci_allow_0_address = true;
 
     fwc->get_dev_path = spapr_get_fw_dev_path;
     nc->nmi_monitor_handler = spapr_nmi;
diff --git a/include/hw/boards.h b/include/hw/boards.h
index 2aec9cb..3f84afd 100644
--- a/include/hw/boards.h
+++ b/include/hw/boards.h
@@ -100,7 +100,8 @@ struct MachineClass {
         no_cdrom:1,
         no_sdcard:1,
         has_dynamic_sysbus:1,
-        no_tco:1;
+        no_tco:1,
+        pci_allow_0_address:1;
     int is_default;
     const char *default_machine_opts;
     const char *default_boot_order;
-- 
2.1.0