Created attachment 488813 [details]
Variation of the patch posted upstream to use cpuid 4 rather than cpuid 2 when possible

Description of problem:
  The mechanism that sysconf(3) uses to get the various CACHE parameters
  fails on the Xen 5670

Version-Release number of selected component (if applicable): 2.12-1.7.el6_0.4

How reproducible:
  Every time

Steps to Reproduce:
1.  Find a machine whose /proc/cpuinfo starts something like this:

  vendor_id       : GenuineIntel
  cpu family      : 6
  model           : 44
  model name      : Intel(R) Xeon(R) CPU           X5670  @ 2.93GHz
  stepping        : 2

2. run "getconf -a | grep CACHE"
3. Observe values printed
  
Actual results:
  All the cache parameter values are zero.

Expected results:
  Non-zero values for all but the level 4 cache

Additional info:
  Recent CPUs no longer have useful cpuid leaf 2 cache descriptors.  For this
  particular machine, cpuid 2 returns 0x55035a01 0xf0b2ff 0x0 0xca0000 in eax,
  ebx, ecx and edx respectively.  The 0xff in the least significant byte of
  ebx indicates that you need to use cpuid leaf 4.  Actually, for all but
  somewhat old CPUs you're better off using cpuid leaf 4 anyway (the only
  machines I have access to that have a cpuid level less than four are a
  "Intel(R) Pentium(R) 4 CPU 1.70GHz" and "Intel(R) Pentium(R) 4 CPU 2.40GHz"
  both of which are long past their use-by date).