<snip>
Another potential explanations of why this doesn't work I could come up
with:
1) Perhaps volk somehow erroneously interprets cpuid info and assumes
that AVX is present, while it is no...? Tom, can you point out the
specific code in volk that is responsible for deciding whether to use
AVX or not?
Your CPU has AVX capability, no doubt about it. I agree with Tom that it's likely that Xen is disabling AVX support with XSETVB -- I'm not sure why it does that. Normal people do not disable extended instruction sets on new processors. It's just turning off silicon you paid for, after all. =)
Attached is a patch for Volk which performs the additional step of verifying AVX with XGETBV to determine that the OS is not turning off useful things. This doesn't fix the fact that Xen is busted, it just won't run AVX instructions when the instructions are disabled.
Joanna, please test this patch for me and verify that your Volk machine enumerates as sse4_2_64. Thanks!
Tom, the patch is available (based on latest master) at github/bistromath:gnuradio.git on the xgetbv branch.
--n
xgetbv.patch