9:06 a.m.
Both pcie-to-pci-bridge and dmi-to-pci-bridge can be used to
create a traditional PCI topology in a pure PCIe guest such as
those using the x86_64/q35 or aarch64/virt machine type;
however, the former should be preferred, as it doesn't need to
obey limitation of real hardware and is completely
architecture-agnostic.
Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1520821
Signed-off-by: Andrea Bolognani <abologna(a)redhat.com>
---
src/conf/domain_addr.c | 59 +++++++++++++++++++++++++++++++++++++++++---------
1 file changed, 49 insertions(+), 10 deletions(-)
diff --git a/src/conf/domain_addr.c b/src/conf/domain_addr.c
index b0709f8295..8964973e03 100644
--- a/src/conf/domain_addr.c
+++ b/src/conf/domain_addr.c
@@ -416,6 +416,7 @@ virDomainPCIAddressSetGrow(virDomainPCIAddressSetPtr addrs,
size_t i;
int model;
bool needDMIToPCIBridge = false;
+ bool needPCIeToPCIBridge = false;
add = addr->bus - addrs->nbuses + 1;
if (add <= 0)
@@ -436,27 +437,41 @@ virDomainPCIAddressSetGrow(virDomainPCIAddressSetPtr addrs,
model = VIR_DOMAIN_CONTROLLER_MODEL_PCI_BRIDGE;
/* if there aren't yet any buses that will accept a
- * pci-bridge, and the caller is asking for one, we'll need to
- * add a dmi-to-pci-bridge first.
+ * pci-bridge, but we need one for the device's PCI address
+ * to make sense, it means the guest only has a PCIe topology
+ * configured so far, and we need to create a traditional PCI
+ * topology to accomodate the new device.
*/
needDMIToPCIBridge = true;
+ needPCIeToPCIBridge = true;
for (i = 0; i < addrs->nbuses; i++) {
if (addrs->buses[i].flags & VIR_PCI_CONNECT_TYPE_PCI_BRIDGE) {
needDMIToPCIBridge = false;
+ needPCIeToPCIBridge = false;
break;
}
}
- if (needDMIToPCIBridge && add == 1) {
+
+ /* Prefer pcie-to-pci-bridge, fall back to dmi-to-pci-bridge */
+ if (addrs->isPCIeToPCIBridgeSupported)
+ needDMIToPCIBridge = false;
+ else
+ needPCIeToPCIBridge = false;
+
+ if ((needDMIToPCIBridge || needPCIeToPCIBridge) && add == 1) {
/* We need to add a single pci-bridge to provide the bus
* our legacy PCI device will be plugged into; however, we
* have also determined that there isn't yet any proper
- * place to connect that pci-bridge we're about to add (on
- * a system with pcie-root, that "proper place" would be a
- * dmi-to-pci-bridge". So, to give the pci-bridge a place
- * to connect, we increase the count of buses to add,
- * while also incrementing the bus number in the address
- * for the device (since the pci-bridge will now be at an
- * index 1 higher than the caller had anticipated).
+ * place to connect that pci-bridge we're about to add,
+ * which means we're dealing with a pure PCIe guest. We
+ * need to create a traditional PCI topology, and for that
+ * we have two options: dmi-to-pci-bridge + pci-bridge or
+ * pcie-root-port + pcie-to-pci-bridge (the latter of which
+ * is pretty much a pci-bridge as far as devices attached
+ * to it are concerned and as such makes the pci-bridge
+ * unnecessary). Either way, there's going to be one more
+ * controller than initially expected, and the 'bus' part
+ * of the device's address will need to be bumped.
*/
add++;
addr->bus++;
@@ -525,6 +540,30 @@ virDomainPCIAddressSetGrow(virDomainPCIAddressSetPtr addrs,
}
}
+ if (needPCIeToPCIBridge) {
+ /* We need a pcie-root-port to plug pcie-to-pci-bridge into; however,
+ * qemuDomainAssignPCIAddresses() will, in some cases, create a dummy
+ * PCIe device and reserve an address for it in order to leave the
+ * user with an empty pcie-root-port ready for hotplugging, and if
+ * we didn't do anything other than adding the pcie-root-port here
+ * it would be used for that, which we don't want. So we change the
+ * connect flags to make sure only the pcie-to-pci-bridge will be
+ * connected to the pcie-root-port we just added, and another one
+ * will be allocated for the dummy PCIe device later on.
+ */
+ if (virDomainPCIAddressBusSetModel(&addrs->buses[i],
+ VIR_DOMAIN_CONTROLLER_MODEL_PCIE_ROOT_PORT)
< 0) {
+ return -1;
+ }
+ addrs->buses[i].flags = VIR_PCI_CONNECT_TYPE_PCIE_TO_PCI_BRIDGE;
+ i++;
+
+ if (virDomainPCIAddressBusSetModel(&addrs->buses[i++],
+
VIR_DOMAIN_CONTROLLER_MODEL_PCIE_TO_PCI_BRIDGE) < 0) {
+ return -1;
+ }
+ }
+
for (; i < addrs->nbuses; i++) {
if (virDomainPCIAddressBusSetModel(&addrs->buses[i], model) < 0)
return -1;
--
2.14.3