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qemu: only force an available legacy-PCI slot on domains with pci-root

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Andrea had the right idea when he disabled the "reserve an extra
unused slot" bit for aarch64/virt. For *any* PCI Express-based
machine, it is pointless since 1) an extra legacy-PCI slot can't be
used for hotplug, since hotplug into legacy PCI slots doesn't work on
PCI Express machinetypes, and 2) even for "coldplug" expansion,
everybody will want to expand using Express controllers, not legacy
PCI.

This patch eliminates the extra slot reserve unless the system has a
pci-root (i.e. legacy PCI)
This commit is contained in:
Laine Stump 2016-09-19 14:17:59 -04:00
parent 5266426b21
commit b2c887844f
1 changed files with 35 additions and 23 deletions
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58
src/qemu/qemu_domain_address.c
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@ -1780,7 +1780,6 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
int nbuses = 0; int nbuses = 0;
size_t i; size_t i;
int rv; int rv;
bool buses_reserved = true;
for (i = 0; i < def->ncontrollers; i++) { for (i = 0; i < def->ncontrollers; i++) {
virDomainControllerDefPtr cont = def->controllers[i]; virDomainControllerDefPtr cont = def->controllers[i];
@ -1802,13 +1801,6 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
if (nbuses > 0 && if (nbuses > 0 &&
virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_PCI_BRIDGE)) { virQEMUCapsGet(qemuCaps, QEMU_CAPS_DEVICE_PCI_BRIDGE)) {
/* This is a dummy info used to reserve a slot for a legacy
* PCI device that doesn't exist, but may in the future, e.g.
* if another device is hotplugged into the domain.
*/
virDomainDeviceInfo info;
info.pciConnectFlags = VIR_PCI_CONNECT_TYPE_PCI_DEVICE;
/* 1st pass to figure out how many PCI bridges we need */ /* 1st pass to figure out how many PCI bridges we need */
if (!(addrs = qemuDomainPCIAddressSetCreate(def, nbuses, true))) if (!(addrs = qemuDomainPCIAddressSetCreate(def, nbuses, true)))
@ -1818,23 +1810,43 @@ qemuDomainAssignPCIAddresses(virDomainDefPtr def,
addrs) < 0) addrs) < 0)
goto cleanup; goto cleanup;
for (i = 0; i < addrs->nbuses; i++) { /* For domains that have pci-root, reserve 1 extra slot for a
if (!qemuDomainPCIBusFullyReserved(&addrs->buses[i])) * (potential) bridge (for future expansion) only if buses are
buses_reserved = false; * not fully reserved yet (if all buses are fully reserved
} * with manually/previously assigned addresses, any attempt to
* reserve an extra slot would fail anyway. But if all buses
/* Reserve 1 extra slot for a (potential) bridge only if buses * are *not* fully reserved, this extra reservation might push
* are not fully reserved yet. * the config to add a new pci-bridge to plug into the final
* available slot, thus preserving the ability to expand)
* *
* We don't reserve the extra slot for aarch64 mach-virt guests * We only do this for those domains that have pci-root, since
* either because we want to be able to have pure virtio-mmio * those with pcie-root will usually want to expand using PCIe
* guests, and reserving this slot would force us to add at least * controllers, which we will do after assigning addresses for
* a dmi-to-pci-bridge to an otherwise PCI-free topology * all *actual* devices.
*/ */
if (!buses_reserved &&
!qemuDomainMachineIsVirt(def) && if (qemuDomainMachineHasPCIRoot(def)) {
qemuDomainPCIAddressReserveNextSlot(addrs, &info) < 0) /* This is a dummy info used to reserve a slot for a
goto cleanup; * legacy PCI device that doesn't exist, but may in the
* future, e.g. if another device is hotplugged into the
* domain.
*/
virDomainDeviceInfo info = {
.pciConnectFlags = (VIR_PCI_CONNECT_HOTPLUGGABLE |
VIR_PCI_CONNECT_TYPE_PCI_DEVICE)
};
bool buses_reserved = true;
for (i = 0; i < addrs->nbuses; i++) {
if (!qemuDomainPCIBusFullyReserved(&addrs->buses[i])) {
buses_reserved = false;
break;
}
}
if (!buses_reserved &&
qemuDomainPCIAddressReserveNextSlot(addrs, &info) < 0)
goto cleanup;
}
if (qemuDomainAssignDevicePCISlots(def, qemuCaps, addrs) < 0) if (qemuDomainAssignDevicePCISlots(def, qemuCaps, addrs) < 0)
goto cleanup; goto cleanup;