Bug 180135

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Description of problem:
In order to boot up IA32 Xen0, I have to add pci=noacpi as the boot 
parameters of Xen0 kernel, or system will hang when initial PCI.

My test machine mainboard is Intel 915.
It can support x86 and x86-64 modes.
Its BIOS firmware ID is:
VVTGDI6A.86A.8039.2005.0516.0949

Its CPU is HT enabled. 
Processor serial: 0000-0F46-0000-0000-0000-0000

# cat /proc/cpuinfo
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Genuine Intel(R) CPU 3.80GHz
stepping        : 6
cpu MHz         : 3793.088
cache size      : 2048 KB
fdiv_bug        : no
hlt_bug         : yes
f00f_bug        : no
coma_bug        : no
fpu             : yes
fpu_exception   : yes
cpuid level     : 5
wp              : yes
flags           : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 cid cx16 xtpr lahf_lm
bogomips        : 9490.72


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


How reproducible:
Always

Steps to Reproduce:
1. Install FC5-Test2
2. Install Xen RPMs
3. Reboot Machine and select to Xen.

Actual Results:  If not give extra pci=noacpi, xen0 boot will hang at initial PCI. And after give pci=noacpi, Xen0 can boot up.

Additional info: