On Mon, 1 Feb 2021 16:59:33 -0800 Ben Widawsky <ben.widaw...@intel.com> wrote:
> Currently, QEMU makes _UID equivalent to the bus number (_BBN). While > there is nothing wrong with doing it this way, CXL spec has a heavy > reliance on _UID to identify host bridges and there is no link to the > bus number. Having a distinct UID solves two problems. The first is it > gets us around the limitation of 256 (current max bus number). The > second is it allows us to replicate hardware configurations where bus > number and uid aren't equivalent. The latter has benefits for our > development and debugging using QEMU. > > The other way to do this would be to implement the expanded bus > numbering, but having an explicit uid makes more sense when trying to > replicate real hardware configurations. > > The QEMU commandline to utilize this would be: > -device pxb-cxl,id=cxl.0,bus="pcie.0",bus_nr=1,uid=x > > Signed-off-by: Ben Widawsky <ben.widaw...@intel.com> > > -- > > I'm guessing this patch will be somewhat controversial. For early CXL > work, this can be dropped without too much heartache. Whilst I'm not personally against, this maybe best to drop for now as you say. > --- > hw/i386/acpi-build.c | 3 ++- > hw/pci-bridge/pci_expander_bridge.c | 19 +++++++++++++++++++ > hw/pci/pci.c | 11 +++++++++++ > include/hw/pci/pci.h | 1 + > include/hw/pci/pci_bus.h | 1 + > 5 files changed, 34 insertions(+), 1 deletion(-) > > diff --git a/hw/i386/acpi-build.c b/hw/i386/acpi-build.c > index cf6eb54c22..145a503e92 100644 > --- a/hw/i386/acpi-build.c > +++ b/hw/i386/acpi-build.c > @@ -1343,6 +1343,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > QLIST_FOREACH(bus, &bus->child, sibling) { > uint8_t bus_num = pci_bus_num(bus); > uint8_t numa_node = pci_bus_numa_node(bus); > + int32_t uid = pci_bus_uid(bus); > > /* look only for expander root buses */ > if (!pci_bus_is_root(bus)) { > @@ -1356,7 +1357,7 @@ build_dsdt(GArray *table_data, BIOSLinker *linker, > scope = aml_scope("\\_SB"); > dev = aml_device("PC%.02X", bus_num); > aml_append(dev, aml_name_decl("_BBN", aml_int(bus_num))); > - init_pci_acpi(dev, bus_num, pci_bus_is_express(bus) ? PCIE : > PCI); > + init_pci_acpi(dev, uid, pci_bus_is_express(bus) ? PCIE : PCI); > > if (numa_node != NUMA_NODE_UNASSIGNED) { > aml_append(dev, aml_name_decl("_PXM", aml_int(numa_node))); > diff --git a/hw/pci-bridge/pci_expander_bridge.c > b/hw/pci-bridge/pci_expander_bridge.c > index b42592e1ff..5021b60435 100644 > --- a/hw/pci-bridge/pci_expander_bridge.c > +++ b/hw/pci-bridge/pci_expander_bridge.c > @@ -67,6 +67,7 @@ struct PXBDev { > > uint8_t bus_nr; > uint16_t numa_node; > + int32_t uid; > }; > > static PXBDev *convert_to_pxb(PCIDevice *dev) > @@ -98,12 +99,20 @@ static uint16_t pxb_bus_numa_node(PCIBus *bus) > return pxb->numa_node; > } > > +static int32_t pxb_bus_uid(PCIBus *bus) > +{ > + PXBDev *pxb = convert_to_pxb(bus->parent_dev); > + > + return pxb->uid; > +} > + > static void pxb_bus_class_init(ObjectClass *class, void *data) > { > PCIBusClass *pbc = PCI_BUS_CLASS(class); > > pbc->bus_num = pxb_bus_num; > pbc->numa_node = pxb_bus_numa_node; > + pbc->uid = pxb_bus_uid; > } > > static const TypeInfo pxb_bus_info = { > @@ -329,6 +338,7 @@ static Property pxb_dev_properties[] = { > /* Note: 0 is not a legal PXB bus number. */ > DEFINE_PROP_UINT8("bus_nr", PXBDev, bus_nr, 0), > DEFINE_PROP_UINT16("numa_node", PXBDev, numa_node, NUMA_NODE_UNASSIGNED), > + DEFINE_PROP_INT32("uid", PXBDev, uid, -1), > DEFINE_PROP_END_OF_LIST(), > }; > > @@ -400,12 +410,21 @@ static const TypeInfo pxb_pcie_dev_info = { > > static void pxb_cxl_dev_realize(PCIDevice *dev, Error **errp) > { > + PXBDev *pxb = convert_to_pxb(dev); > + > /* A CXL PXB's parent bus is still PCIe */ > if (!pci_bus_is_express(pci_get_bus(dev))) { > error_setg(errp, "pxb-cxl devices cannot reside on a PCI bus"); > return; > } > > + if (pxb->uid < 0) { > + error_setg(errp, "pxb-cxl devices must have a valid uid > (0-2147483647)"); > + return; > + } > + > + /* FIXME: Check that uid doesn't collide with UIDs of other host bridges > */ > + > pxb_dev_realize_common(dev, CXL, errp); > } > > diff --git a/hw/pci/pci.c b/hw/pci/pci.c > index adbe8aa260..bf019d91a0 100644 > --- a/hw/pci/pci.c > +++ b/hw/pci/pci.c > @@ -170,6 +170,11 @@ static uint16_t pcibus_numa_node(PCIBus *bus) > return NUMA_NODE_UNASSIGNED; > } > > +static int32_t pcibus_uid(PCIBus *bus) > +{ > + return -1; > +} > + > static void pci_bus_class_init(ObjectClass *klass, void *data) > { > BusClass *k = BUS_CLASS(klass); > @@ -184,6 +189,7 @@ static void pci_bus_class_init(ObjectClass *klass, void > *data) > > pbc->bus_num = pcibus_num; > pbc->numa_node = pcibus_numa_node; > + pbc->uid = pcibus_uid; > } > > static const TypeInfo pci_bus_info = { > @@ -530,6 +536,11 @@ int pci_bus_numa_node(PCIBus *bus) > return PCI_BUS_GET_CLASS(bus)->numa_node(bus); > } > > +int pci_bus_uid(PCIBus *bus) > +{ > + return PCI_BUS_GET_CLASS(bus)->uid(bus); > +} > + > static int get_pci_config_device(QEMUFile *f, void *pv, size_t size, > const VMStateField *field) > { > diff --git a/include/hw/pci/pci.h b/include/hw/pci/pci.h > index bde3697bee..a46de48ccd 100644 > --- a/include/hw/pci/pci.h > +++ b/include/hw/pci/pci.h > @@ -463,6 +463,7 @@ static inline int pci_dev_bus_num(const PCIDevice *dev) > } > > int pci_bus_numa_node(PCIBus *bus); > +int pci_bus_uid(PCIBus *bus); > void pci_for_each_device(PCIBus *bus, int bus_num, > void (*fn)(PCIBus *bus, PCIDevice *d, void *opaque), > void *opaque); > diff --git a/include/hw/pci/pci_bus.h b/include/hw/pci/pci_bus.h > index eb94e7e85c..3c9fbc55bb 100644 > --- a/include/hw/pci/pci_bus.h > +++ b/include/hw/pci/pci_bus.h > @@ -17,6 +17,7 @@ struct PCIBusClass { > > int (*bus_num)(PCIBus *bus); > uint16_t (*numa_node)(PCIBus *bus); > + int32_t (*uid)(PCIBus *bus); > }; > > enum PCIBusFlags {