>> I am attempting to run Xen on an AMD FX-4170 Quad-Core Processor.
>> I have installed Fedora 17 to serve as Dom0.
>> 
>> I am finding that Python does not run well on this
>> configuration. Specifically, "import random" causes the Python interpreter
>> to terminate with "Illegal instruction". This means that xend and yum will
>> not run.
>> 
>> I filed a bug under yum [1], but just realized that things work if I
>> boot Fedora 17 on bare metal.
>> 
>> Under Xen, /proc/cpuinfo reports the following flags:
>> 
>> fpu de tsc msr pae cx8 apic cmov pat clflush mmx fxsr sse sse2 ht syscall
>> nx mmxext fxsr_opt lm constant_tsc rep_good nopl nonstop_tsc extd_apicid
>> aperfmperf pni pclmulqdq ssse3 cx16 sse4_1 sse4_2 popcnt aes hypervisor
>> lahf_lm cmp_legacy extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch
>> xop fma4 perfctr_core arat cpb hw_pstate
>> 
>> Has anyone had similar trouble?
 
> No. But it sounds like the AVX disaster.
> 
> https://bugzilla.redhat.com/show_bug.cgi?id=801650

It seems to be.

I booted bare metal and used yum to install gdb and the debug symbols
for Python and glibc.

Then I rebooted in Xen. I found that gdb itself crashed when the debug
symbols were installed, so I removed them. I ran gdb again and obtained
a partial backtrace on "import random":

(gdb) ba
#0  0x00007ffff71474ec in __ieee754_exp_fma4 () from /lib64/libm.so.6
#1  0x00007ffff009e415 in ?? () from /usr/lib64/python2.7/lib-dynload/math.so
#2  0x00007ffff7b00053 in PyEval_EvalFrameEx () from /lib64/libpython2.7.so.1.0
#3  0x00007ffff7b00b2f in PyEval_EvalCodeEx () from /lib64/libpython2.7.so.1.0
#4  0x00007ffff7b00c02 in PyEval_EvalCode () from /lib64/libpython2.7.so.1.0
#5  0x00007ffff7b1017d in PyImport_ExecCodeModuleEx () from 
/lib64/libpython2.7.so.1.0
[...]

After looking a little closer, it seems that __ieee754_exp_fma4 is
executing "vmovsd %xmm0,-0x20(%rsp)".

I thought booting Xen with xsave=1 might help, but this causes Xen to
crash on this hardware. As mentioned above, it looks like there has been
work in glibc to properly detect AVX (my understanding is that you have
to check that both the processor and OS supports it). Is it possible
that this glibc work missed something?

-- 
Mike

:wq
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