> -----Original Message----- > From: Knut Omang [mailto:knut.om...@oracle.com] > Subject: Re: [Qemu-devel] [PATCH v2 2/2] pci: add check for pcie root ports > and > downstream ports > > On Thu, 2014-08-21 at 17:47 +0800, arei.gong...@huawei.com wrote: > > From: Gonglei <arei.gong...@huawei.com> > > > > If ARI Forwarding is disabled, according to PCIe spec > > section 7.3.1, only slot 0 with the device attached to > > logic bus representing the link from downstream > > ports and root ports. > > > > So, adding check for PCIe downstream ports and root ports, > > which avoid useless operation, both hotplug and coldplug. > > > > Signed-off-by: Gonglei <arei.gong...@huawei.com> > > --- > > hw/pci/pci.c | 51 > +++++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 51 insertions(+) > > > > diff --git a/hw/pci/pci.c b/hw/pci/pci.c > > index daeaeac..aa0af0c 100644 > > --- a/hw/pci/pci.c > > +++ b/hw/pci/pci.c > > @@ -773,6 +773,52 @@ static int pci_init_multifunction(PCIBus *bus, > PCIDevice *dev) > > return 0; > > } > > > > +static int pci_check_pcie_port(PCIBus *bus, PCIDevice *dev) > > +{ > > + Object *obj = OBJECT(bus); > > + > > + if (pci_bus_is_root(bus)) { > > + return 0; > > + } > > + > > + if (object_dynamic_cast(obj, TYPE_PCIE_BUS)) { > > + DeviceState *parent = qbus_get_parent(BUS(obj)); > > + PCIDevice *pci_dev = PCI_DEVICE(parent); > > + uint8_t port_type; > > + /* > > + * Root ports and downstream ports of switches are the hot > > + * pluggable ports in a PCI Express hierarchy. > > + * PCI Express supports chip-to-chip interconnect, a PCIe link can > > + * only connect one pci device/Switch/EndPoint or PCI-bridge. > > + * > > + * 7.3. Configuration Transaction Rules (PCI Express specification > 3.0) > > + * 7.3.1. Device Number > > + * > > + * Downstream Ports that do not have ARI Forwarding enabled > must > > + * associate only Device 0 with the device attached to the Logical > Bus > > + * representing the Link from the Port. > > + * > > + * If ARI Forwarding is not enabled on root ports and downstream > > + * ports, only support the devices with slot non-0, regardless of > > + * hotplug or coldplug. > > + */ > > My interpretation of this section of the spec is that if ARI forwarding > is not available, only the normal 8 functions can be accessed for each > device, eg. device/functions 0.0 -> 0.7 - if a device has more than 8 > functions, it will need the second device's namespace, eg. devfn 1.0++, > which would not be routed correctly in a non-ari forward capable device. > Yes.
> As far as I understand, with this fix you restrict an non-ARI capable > switch to only expose one device? > Yes. Otherwise it will confuse users who configure a device with 'slot > 0 ', and the interface return OK, but the guest os report errors as below: [ 159.035250] Pciehp 0000:05:00.0:pcie24: Button pressed on Slot (0 - 4) [ 159.035274] Pciehp 0000:05:00.0:pcie24: Card present on Slot (0 - 4) [ 159.036517] Pciehp 0000:05:00.0:pcie24: PCI slot #0 - 4 - powering on due to button press. [ 159.188049] Pciehp 0000:05:00.0:pcie24: Failed to check link status [ 159.201968] Pciehp 0000:05:00.0:pcie24: Card not present on Slot (0 - 4) [ 159.202529] Pciehp 0000:05:00.0:pcie24: Already disabled on Slot (0 - 4) Best regards, -Gonglei > Knut > > > + port_type = pcie_cap_get_type(pci_dev); > > + if (port_type == PCI_EXP_TYPE_DOWNSTREAM || > > + port_type == PCI_EXP_TYPE_ROOT_PORT) { > > + if (!pcie_cap_is_ari_enabled(pci_dev)) { > > + if (PCI_SLOT(dev->devfn) != 0) { > > + error_report("PCIe: Port's ARI Forwarding is > disabled, " > > + "device can't be populated in > slot %d", > > + PCI_SLOT(dev->devfn)); > > + return -1; > > + } > > + } > > + } > > + } > > + > > + return 0; > > +} > > + > > static void pci_config_alloc(PCIDevice *pci_dev) > > { > > int config_size = pci_config_size(pci_dev); > > @@ -827,6 +873,11 @@ static PCIDevice > *do_pci_register_device(PCIDevice *pci_dev, PCIBus *bus, > > > > pci_dev->bus = bus; > > pci_dev->devfn = devfn; > > + > > + if (pci_check_pcie_port(bus, pci_dev)) { > > + return NULL; > > + } > > + > > dma_as = pci_device_iommu_address_space(pci_dev); > > > > memory_region_init_alias(&pci_dev->bus_master_enable_region, >