Comment 21 for bug 883441

Oneiric SRU Justification:

Impact:

commit 64b3db22c04586997ab4be46dd5a5b99f8a2d390 (2.6.39),
"Remove use of unreliable FADT revision field" caused a regression
for old P4 systems because now cst_control and other fields are
not reset to 0.

        The effect is that acpi_processor_power_init will notice
cst_control != 0 and a write to CST_CNT register is performed
that should not happen. As result, the system oopses after the
"No _CST, giving up" message, sometimes in acpi_ns_internalize_name,
sometimes in acpi_ns_get_type, usually at random places. May be
during migration to CPU 1 in acpi_processor_get_throttling.

        Every one of these settings help to avoid this problem:
 - acpi=off
 - processor.nocst=1
 - maxcpus=1

Fix:

Apply upstream commit 3e80acd1af40fcd91a200b0416a7616b20c5d647

Testcase:

Without the fix, machines are effectively unbootable unless acpi=off or processor.nocst=1 or maxcpus=1 is used. With the fix the system will boot.