Hi Michael, On Mon, Sep 27, 2021 at 12:49 PM Michael S. Tsirkin <m...@redhat.com> wrote:
> On Mon, Sep 27, 2021 at 10:33:42AM +0100, Daniel P. Berrangé wrote: > > 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]. > > > Indeed, oops. Thanks for the report! > > Going back and looking at seabios code, didn't we get confused? > Shouldn't we have reserved memory and not IO? > We need the IO space for the legacy PCI bridges, otherwise an empty PCI bridge will become unusable. > > I see: > int resource_optional = pcie_cap && (type == > PCI_REGION_TYPE_IO); > if (!sum && hotplug_support && !resource_optional) > sum = align; /* reserve min size for hot-plug */ > > > generally maybe we should just add an ACPI-hotplug capability and > teach seabios about it? > I suppose it is possible. Thanks, Marcel > > Marcel? > > > > 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 :| > >
