[Bug 956051] Re: libc6 crash while running 'xm'

[jwestfall]

Hi

It appears this issue can be worked around by adding the following
options to xen's command line in grub.

cpuid_mask_ext_ecx=0xFFFEFFF cpuid_mask_ecx=0xEFFFFFF

This masks both FMA4 and AVX from cpuid for dom0 and all domU's

Also note that xen has a cpuid option for domU configs that allows to
you mask these as well, but it doesn't seem to work for userspace making
direct cpuid calls.  The kernel will see that fma4 isn't there, but
glibc still see's it as available and you get crashes.

jim

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https://bugs.launchpad.net/bugs/956051

Title:
  libc6 crash while running 'xm'

Status in “eglibc” package in Ubuntu:
  Confirmed

Bug description:
  Ubuntu Version: 12.04 (precise)

  libc6: 2.15-0ubuntu5
  xen-hypervisor-4.1-amd64: 4.1.2-2ubuntu2
  linux-image-generic: 3.2.0.18.20

  Everytime I try to run 'xm list' on a new AMD Opteron 6274 system (Bulldozer architecture) I'm getting a crash.
  I couldn't even file a bug report through "apport-bug".
  Repeating the same procedure with Ubuntu Oneiric showed no problems at all.

  dmesg showed following messages:

  [  479.891581] xm[1746] trap invalid opcode ip:7fd684f8a5fc sp:7fff3ebb3c70 error:0 in libm-2.15.so[7fd684f48000+f9000]
  [  479.937611] apport[1758] trap invalid opcode ip:7fd6cb9ea5fc sp:7fff9bbc06b0 error:0 in libm-2.15.so[7fd6cb9a8000+f9000]
  [  479.937641] Process 1758(apport) has RLIMIT_CORE set to 1
  [  479.937645] Aborting core

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