On Wed, Sep 29, 2021 at 04:41:49PM +0300, Marcel Apfelbaum wrote:
> 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.
Maybe we should go back to using OSC then ... the issue
is we can't then mix acpi and native hotplug for bridges.
>
>
> 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
> > --
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>
