Re: [PATCH v2] PCI: acpiphp: Reassign resources on bridge if necessary

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, May 22, 2023 at 01:52:33PM +0200, Rafael J. Wysocki wrote:
> On Mon, May 22, 2023 at 1:06 PM Igor Mammedov <imammedo@redhat.com> wrote:
> >
> > On Mon, 24 Apr 2023 21:15:57 +0200
> > Igor Mammedov <imammedo@redhat.com> wrote:
> >
> > > When using ACPI PCI hotplug, hotplugging a device with
> > > large BARs may fail if bridge windows programmed by
> > > firmware are not large enough.
> >
> > Rafael,
> >
> > Since there was no more comments for a while,
> > can you merge this patch through your tree?
> 
> I need an ACK from Bjorn on this, as the PCI maintainer, or it can go
> in via the PCI tree as far as I'm concerned.
> 
> Thanks!

I'd also like an ACK for:
Cc: stable@vger.kernel.org



> > > Reproducer:
> > >   $ qemu-kvm -monitor stdio -M q35  -m 4G \
> > >       -global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=on \
> > >       -device id=rp1,pcie-root-port,bus=pcie.0,chassis=4 \
> > >       disk_image
> > >
> > >  wait till linux guest boots, then hotplug device
> > >    (qemu) device_add qxl,bus=rp1
> > >
> > >  hotplug on guest side fails with:
> > >    pci 0000:01:00.0: [1b36:0100] type 00 class 0x038000
> > >    pci 0000:01:00.0: reg 0x10: [mem 0x00000000-0x03ffffff]
> > >    pci 0000:01:00.0: reg 0x14: [mem 0x00000000-0x03ffffff]
> > >    pci 0000:01:00.0: reg 0x18: [mem 0x00000000-0x00001fff]
> > >    pci 0000:01:00.0: reg 0x1c: [io  0x0000-0x001f]
> > >    pci 0000:01:00.0: BAR 0: no space for [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 0: failed to assign [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 1: no space for [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 1: failed to assign [mem size 0x04000000]
> > >    pci 0000:01:00.0: BAR 2: assigned [mem 0xfe800000-0xfe801fff]
> > >    pci 0000:01:00.0: BAR 3: assigned [io  0x1000-0x101f]
> > >    qxl 0000:01:00.0: enabling device (0000 -> 0003)
> > >    Unable to create vram_mapping
> > >    qxl: probe of 0000:01:00.0 failed with error -12
> > >
> > > However when using native PCIe hotplug
> > >   '-global ICH9-LPC.acpi-pci-hotplug-with-bridge-support=off'
> > > it works fine, since kernel attempts to reassign unused resources.
> > > Use the same machinery as native PCIe hotplug to (re)assign resources.
> > >
> > > Signed-off-by: Igor Mammedov <imammedo@redhat.com>
> > > ---
> > > tested in QEMU with Q35 machine on PCIE root port and also
> > > with nested conventional bridge attached to root port.
> > >
> > > v2:
> > >   * fixup subject to match expected style
> > >   * drop no longer needed __pci_bus_size_bridges() to avoid
> > >     memory leak (Bjorn Helgaas <helgaas@kernel.org>)
> > > ---
> > >  drivers/pci/hotplug/acpiphp_glue.c | 5 +----
> > >  1 file changed, 1 insertion(+), 4 deletions(-)
> > >
> > > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> > > index 5b1f271c6034..328d1e416014 100644
> > > --- a/drivers/pci/hotplug/acpiphp_glue.c
> > > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> > > @@ -498,7 +498,6 @@ static void enable_slot(struct acpiphp_slot *slot, bool bridge)
> > >                               acpiphp_native_scan_bridge(dev);
> > >               }
> > >       } else {
> > > -             LIST_HEAD(add_list);
> > >               int max, pass;
> > >
> > >               acpiphp_rescan_slot(slot);
> > > @@ -512,12 +511,10 @@ static void enable_slot(struct acpiphp_slot *slot, bool bridge)
> > >                               if (pass && dev->subordinate) {
> > >                                       check_hotplug_bridge(slot, dev);
> > >                                       pcibios_resource_survey_bus(dev->subordinate);
> > > -                                     __pci_bus_size_bridges(dev->subordinate,
> > > -                                                            &add_list);
> > >                               }
> > >                       }
> > >               }
> > > -             __pci_bus_assign_resources(bus, &add_list, NULL);
> > > +             pci_assign_unassigned_bridge_resources(bus->self);
> > >       }
> > >
> > >       acpiphp_sanitize_bus(bus);
> >