pci: Adjust PCI config limit based on bus topology
A conventional PCI bus does not support config space accesses above
the standard 256 byte configuration space. PCIe-to-PCI bridges are
not permitted to forward transactions if the extended register address
field is non-zero and must handle it as an unsupported request (PCIe
bridge spec rev 1.0, 4.1.3, 4.1.4). Therefore, we should not support
extended config space if there is a conventional bus anywhere on the
path to a device.
Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
Reviewed-by: Marcel Apfelbaum <marcel@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
diff --git a/hw/pci/pci_host.c b/hw/pci/pci_host.c
index 5eaa935..5f5345d 100644
--- a/hw/pci/pci_host.c
+++ b/hw/pci/pci_host.c
@@ -20,6 +20,7 @@
#include "qemu/osdep.h"
#include "hw/pci/pci.h"
+#include "hw/pci/pci_bridge.h"
#include "hw/pci/pci_host.h"
#include "hw/pci/pci_bus.h"
#include "trace.h"
@@ -50,9 +51,29 @@
return pci_find_device(bus, bus_num, devfn);
}
+static void pci_adjust_config_limit(PCIBus *bus, uint32_t *limit)
+{
+ if (*limit > PCI_CONFIG_SPACE_SIZE) {
+ if (!pci_bus_is_express(bus)) {
+ *limit = PCI_CONFIG_SPACE_SIZE;
+ return;
+ }
+
+ if (!pci_bus_is_root(bus)) {
+ PCIDevice *bridge = pci_bridge_get_device(bus);
+ pci_adjust_config_limit(pci_get_bus(bridge), limit);
+ }
+ }
+}
+
void pci_host_config_write_common(PCIDevice *pci_dev, uint32_t addr,
uint32_t limit, uint32_t val, uint32_t len)
{
+ pci_adjust_config_limit(pci_get_bus(pci_dev), &limit);
+ if (limit <= addr) {
+ return;
+ }
+
assert(len <= 4);
/* non-zero functions are only exposed when function 0 is present,
* allowing direct removal of unexposed functions.
@@ -71,6 +92,11 @@
{
uint32_t ret;
+ pci_adjust_config_limit(pci_get_bus(pci_dev), &limit);
+ if (limit <= addr) {
+ return ~0x0;
+ }
+
assert(len <= 4);
/* non-zero functions are only exposed when function 0 is present,
* allowing direct removal of unexposed functions.
