From: Igor Mammedov <imammedo@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: marcel@redhat.com, "Peter Maydell" <peter.maydell@linaro.org>,
"Daniel P. Berrangé" <berrange@redhat.com>,
qemu-devel@nongnu.org
Subject: Re: [PULL 1/5] hw/pcie-root-port: Fix hotplug for PCI devices requiring IO
Date: Thu, 30 Sep 2021 10:34:24 +0200 [thread overview]
Message-ID: <20210930103424.5f408978@redhat.com> (raw)
In-Reply-To: <20210929172519-mutt-send-email-mst@kernel.org>
On Wed, 29 Sep 2021 17:47:37 -0400
"Michael S. Tsirkin" <mst@redhat.com> wrote:
> 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 <mst@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.apfelbaum@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 <imammedo@redhat.com>
> > > > Signed-off-by: Marcel Apfelbaum <marcel@redhat.com>
> > > > Message-Id: <20210802090057.1709775-1-marcel@redhat.com>
> > > > Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
> > > > Signed-off-by: Michael S. Tsirkin <mst@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.
How OSC could help with the issue?
> >
> >
> > 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 :|
> >
> >
>
next prev parent reply other threads:[~2021-09-30 8:36 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-03 20:52 [PULL 0/5] pc,pci: bugfixes Michael S. Tsirkin
2021-08-03 20:52 ` [PULL 1/5] hw/pcie-root-port: Fix hotplug for PCI devices requiring IO Michael S. Tsirkin
2021-09-27 9:33 ` Daniel P. Berrangé
2021-09-27 9:49 ` Michael S. Tsirkin
2021-09-29 9:05 ` Daniel P. Berrangé
2021-09-29 13:55 ` Marcel Apfelbaum
2021-09-29 13:41 ` Marcel Apfelbaum
2021-09-29 14:12 ` Gerd Hoffmann
2021-09-29 21:47 ` Michael S. Tsirkin
2021-09-30 8:34 ` Igor Mammedov [this message]
2021-09-30 10:52 ` Michael S. Tsirkin
2021-11-02 9:23 ` Daniel P. Berrangé
2021-11-02 9:33 ` Marcel Apfelbaum
2021-11-02 11:17 ` Julia Suvorova
2021-08-03 20:52 ` [PULL 2/5] acpi: x86: pcihp: add support hotplug on multifunction bridges Michael S. Tsirkin
2021-08-03 20:52 ` [PULL 3/5] arm/acpi: allow DSDT changes Michael S. Tsirkin
2021-08-03 20:52 ` [PULL 4/5] Revert "acpi/gpex: Inform os to keep firmware resource map" Michael S. Tsirkin
2021-08-03 20:52 ` [PULL 5/5] Drop _DSM 5 from expected DSDTs on ARM Michael S. Tsirkin
2021-08-04 15:52 ` [PULL 0/5] pc,pci: bugfixes Peter Maydell
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