Bug 1260913 - [PCIe] Seabios goes into an endless loop when booted with 240 "-device xio3130-downstream"
[PCIe] Seabios goes into an endless loop when booted with 240 "-device xio313...
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: seabios (Show other bugs)
x86_64 Linux
low Severity low
: rc
: ---
Assigned To: Marcel Apfelbaum
Virtualization Bugs
Won't fix
: 1055416 (view as bug list)
Depends On:
Blocks: 1227278
  Show dependency treegraph
Reported: 2015-09-08 04:26 EDT by huiqingding
Modified: 2016-02-24 13:25 EST (History)
8 users (show)

See Also:
Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Story Points: ---
Clone Of:
Last Closed: 2016-01-14 07:05:38 EST
Type: Bug
Regression: ---
Mount Type: ---
Documentation: ---
Verified Versions:
Category: ---
oVirt Team: ---
RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: ---

Attachments (Terms of Use)
qemu-kvm command line (17.35 KB, text/plain)
2015-09-08 04:28 EDT, huiqingding
no flags Details

  None (edit)
Description huiqingding 2015-09-08 04:26:59 EDT
Description of problem:
can not see seabios GUI when boot with 240 "-device xio3130-downstream" via PCIe-switch.
Also test with 239 "-device xio3130-downstream", not hit this issue.

Version-Release number of selected component (if applicable):

How reproducible:

Steps to Reproduce:
1. boot guest with 240 "-device xio3130-downstream"
# sh multi-pcie.sh 240
# cat multi-pcie.sh


CLI="/usr/libexec/qemu-kvm -enable-kvm -M $MACHINE -smp $SMP -m $MEM -name vm1 -drive file=$GUEST_IMG,if=none,id=guest-img,format=$IMG_FORMAT,werror=stop,rerror=stop -device ide-hd,drive=guest-img,bus=ide.0,unit=0,id=os-disk,bootindex=1 -spice port=5932,disable-ticketing -vga qxl  -monitor stdio -qmp tcp:0:6666,server,nowait -boot menu=on -chardev file,path=/home/seabios.log,id=seabios -device isa-debugcon,chardev=seabios,iobase=0x402"

while [ ${i:=0} -lt ${1:-0} ]

    if [ $((dstreamId%32)) -eq 0 ]
        CLI="$CLI -device ioh3420,bus=pcie.0,id=root.$ustreamId,slot=$ustreamId"
        CLI="$CLI -device x3130-upstream,bus=root.$ustreamId,id=upstream$ustreamId"

    CLI="$CLI -device xio3130-downstream,bus=upstream$ustreamId,id=downstream$dstreamId,chassis=$chassisId"



Actual results:
Can not see seabios GUI via remoteview spice://$IP:$port
Using isa-debugcon debug, got the following messages:
SeaBIOS (version seabios-1.7.5-11.el7)
Running on QEMU (q35)
Running on KVM
RamSize: 0x80000000 [cmos]
Relocating init from 0x000e3f59 to 0x7ffb1cd0 (size 57960)
Found QEMU fw_cfg
RamBlock: addr 0x0000000000000000 len 0x0000000080000000 [e820]
RamBlock: addr 0x0000000100000000 len 0x0000000080000000 [e820]
Moving pm_base to 0x600
boot order:
1: /pci@i0cf8/pci8086,2922@1f,2/drive@0/disk@0
CPU Mhz=3396
=== PCI bus & bridge init ===
PCI: pci_bios_init_bus_rec bus = 0x0
PCI: pci_bios_init_bus_rec bdf = 0x18
PCI: primary bus = 0x0
PCI: secondary bus = 0xff -> 0x1
PCI: pci_bios_init_bus_rec bus = 0x1
PCI: pci_bios_init_bus_rec bdf = 0x100
PCI: primary bus = 0x0 -> 0x1
PCI: secondary bus = 0xff -> 0x2
PCI: pci_bios_init_bus_rec bus = 0x2
PCI: pci_bios_init_bus_rec bdf = 0x200
PCI: primary bus = 0x0 -> 0x2
PCI: secondary bus = 0xff -> 0x3
PCI: pci_bios_init_bus_rec bus = 0x3
PCI: subordinate bus = 0x0 -> 0x3
PCI: pci_bios_init_bus_rec bdf = 0x208
PCI: primary bus = 0x0 -> 0x2
PCI: secondary bus = 0xff -> 0x4
PCI: pci_bios_init_bus_rec bus = 0x4
PCI: subordinate bus = 0x0 -> 0x4
PCI: pci_bios_init_bus_rec bdf = 0x210
PCI: primary bus = 0x0 -> 0x2
PCI: secondary bus = 0xff -> 0x5
PCI: pci_bios_init_bus_rec bus = 0x5
PCI: subordinate bus = 0x0 -> 0x5
PCI: pci_bios_init_bus_rec bdf = 0x218
PCI: primary bus = 0x0 -> 0x2
PCI: secondary bus = 0xff -> 0x6
PCI: pci_bios_init_bus_rec bus = 0x6
PCI: subordinate bus = 0x0 -> 0x6
PCI: pci_bios_init_bus_rec bdf = 0x220
PCI: primary bus = 0x0 -> 0x2
PCI: secondary bus = 0xff -> 0x7
PCI: pci_bios_init_bus_rec bus = 0x7
PCI: subordinate bus = 0x0 -> 0x7
PCI: pci_bios_init_bus_rec bdf = 0x228
PCI: primary bus = 0x0 -> 0x2
PCI: secondary bus = 0xff -> 0x8
... ...

Expected results:
can see the seabio GUI and boot guest correctly.

Additional info:
Comment 1 huiqingding 2015-09-08 04:28:53 EDT
Created attachment 1071230 [details]
qemu-kvm command line

The command line of Comment #0 is as the attachment file.
Comment 4 Marcel Apfelbaum 2016-01-04 06:58:41 EST

The problem here is that the maximum bus number can be 255.
The mentioned script creates more than 255 buses when the parameter is > 240
and of course the SeaBIOS cannot continue.

Even if, as explained, this is not a bug, SeaBIOS does go into an endless loop which is not nice.
I posted a fix upstream:
     [SeaBIOS] [PATCH] pci: panic when out of bus numbers
Comment 5 Marcel Apfelbaum 2016-01-14 07:05:38 EST
The patch was rejected by Gerd as being an illegal hardware configuration
and it should not be resolved in firmware, but in QEMU.

After I discussed it with Michael, the QEMU PCI maintainer we decided that we
should not follow this, see comment 4 for details.
Comment 6 Amnon Ilan 2016-02-24 13:25:51 EST
*** Bug 1055416 has been marked as a duplicate of this bug. ***

Note You need to log in before you can comment on or make changes to this bug.