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

Igor Mammedov
2023-04-24T19:16:53Z

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@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);
--
2.39.1