On Tue, 18 Apr 2023 07:08:09 -0400
"Michael S. Tsirkin" <mst@xxxxxxxxxx> wrote:
> On Tue, Apr 18, 2023 at 10:50:30AM +0200, Igor Mammedov wrote:
> > When using ACPI PCI hotplug, hotplugging a device with
> > large BARs may fail if bridge windows programmed by
> > firmware are not large enough.
> >
> > 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@xxxxxxxxxx>
>
> Acked-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
>
> And I think:
>
> Fixes: d66ecb7220a7 ("PCI / ACPI: Use boot-time resource allocation rules during hotplug")
Probably not, this commit basically added pcibios_resource_survey_bus() and
nothing else important. Looking through history it was always broken this way.
>
> > ---
> > tested in QEMU with Q35 machine on PCIE root port and also
> > with nested conventional bridge attached to root port.
> > ---
> > drivers/pci/hotplug/acpiphp_glue.c | 2 +-
> > 1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/pci/hotplug/acpiphp_glue.c b/drivers/pci/hotplug/acpiphp_glue.c
> > index 5b1f271c6034..9aebde28a92f 100644
> > --- a/drivers/pci/hotplug/acpiphp_glue.c
> > +++ b/drivers/pci/hotplug/acpiphp_glue.c
> > @@ -517,7 +517,7 @@ static void enable_slot(struct acpiphp_slot *slot, bool bridge)
> > }
> > }
> > }
> > - __pci_bus_assign_resources(bus, &add_list, NULL);
> > + pci_assign_unassigned_bridge_resources(bus->self);
> > }
> >
> > acpiphp_sanitize_bus(bus);
> > --
> > 2.39.1
>
