Intel microcode update and glibc HLE

[Siddhesh Poyarekar]

Hi,

The microcode_ctl package recently updated itself to include the
latest intel microcode update that disables HLE.  This is resulting in
unbootable Haswell systems on Fedora[1] and elsewhere.  The problem
seems to be that the microcode update is applied a bit late during
every boot.  Due to this, the kernel has stale CPU capabilities and
systemd sees HLE enabled before the microcode update is applied.
Later, HLE is disabled and the next pthread operation in systemd dies
with a SIGILL.

The ideal solution for this would probably be to apply the microcode
update as early as possible during boot, but things get complicated
with suspend-resume or hibernate, so it's not very simple.  In Fedora
we're now rebuilding glibc with elision disabled again since keeping
it enabled is useless and is currently harmful.

Siddhesh

[1] https://bugzilla.redhat.com/show_bug.cgi?id=1146967
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