On Tue, Aug 03, 2021 at 04:52:03PM -0400, Michael S. Tsirkin wrote: > From: Marcel Apfelbaum <marcel.apfelb...@gmail.com> > > Q35 has now ACPI hotplug enabled by default for PCI(e) devices. > As opposed to native PCIe hotplug, guests like Fedora 34 > will not assign IO range to pcie-root-ports not supporting > native hotplug, resulting into a regression. > > Reproduce by: > qemu-bin -M q35 -device pcie-root-port,id=p1 -monitor stdio > device_add e1000,bus=p1 > In the Guest OS the respective pcie-root-port will have the IO range > disabled. > > Fix it by setting the "reserve-io" hint capability of the > pcie-root-ports so the firmware will allocate the IO range instead. > > Acked-by: Igor Mammedov <imamm...@redhat.com> > Signed-off-by: Marcel Apfelbaum <mar...@redhat.com> > Message-Id: <20210802090057.1709775-1-mar...@redhat.com> > Reviewed-by: Michael S. Tsirkin <m...@redhat.com> > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > --- > hw/pci-bridge/gen_pcie_root_port.c | 5 +++++ > 1 file changed, 5 insertions(+)
This change, when combined with the switch to ACPI based hotplug by default, is responsible for a significant regression in QEMU 6.1.0 It is no longer possible to have more than 15 pcie-root-port devices added to a q35 VM in 6.1.0. Before this I've had as many as 80+ devices present before I stopped trying to add more. https://gitlab.com/qemu-project/qemu/-/issues/641 This regression is significant, because it has broken the out of the box default configuration that OpenStack uses for booting all VMs. They add 16 pcie-root-ports by defalt to allow empty slots for device hotplug under q35 [1]. > diff --git a/hw/pci-bridge/gen_pcie_root_port.c > b/hw/pci-bridge/gen_pcie_root_port.c > index ec9907917e..20099a8ae3 100644 > --- a/hw/pci-bridge/gen_pcie_root_port.c > +++ b/hw/pci-bridge/gen_pcie_root_port.c > @@ -28,6 +28,7 @@ OBJECT_DECLARE_SIMPLE_TYPE(GenPCIERootPort, > GEN_PCIE_ROOT_PORT) > (GEN_PCIE_ROOT_PORT_AER_OFFSET + PCI_ERR_SIZEOF) > > #define GEN_PCIE_ROOT_PORT_MSIX_NR_VECTOR 1 > +#define GEN_PCIE_ROOT_DEFAULT_IO_RANGE 4096 > > struct GenPCIERootPort { > /*< private >*/ > @@ -75,6 +76,7 @@ static bool gen_rp_test_migrate_msix(void *opaque, int > version_id) > static void gen_rp_realize(DeviceState *dev, Error **errp) > { > PCIDevice *d = PCI_DEVICE(dev); > + PCIESlot *s = PCIE_SLOT(d); > GenPCIERootPort *grp = GEN_PCIE_ROOT_PORT(d); > PCIERootPortClass *rpc = PCIE_ROOT_PORT_GET_CLASS(d); > Error *local_err = NULL; > @@ -85,6 +87,9 @@ static void gen_rp_realize(DeviceState *dev, Error **errp) > return; > } > > + if (grp->res_reserve.io == -1 && s->hotplug && !s->native_hotplug) { > + grp->res_reserve.io = GEN_PCIE_ROOT_DEFAULT_IO_RANGE; > + } > int rc = pci_bridge_qemu_reserve_cap_init(d, 0, > grp->res_reserve, errp); > > -- > MST > > Regards, Daniel [1] https://github.com/openstack/tripleo-heat-templates/blob/7a6cd0640ec390a330f5699d8ed60f71b2a9f514/deployment/nova/nova-compute-container-puppet.yaml#L462-L472 -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
