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Date: Fri, 30 Mar 2012 09:14:53 -0400
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Subject: Re: [PATCH 04/76] ACPICA: Fix regression in FADT revision checks
From: Josh Boyer <jwboyer@gmail.com>
To: Len Brown <lenb@kernel.org>
Cc: linux-acpi@vger.kernel.org, linux-pm@lists.linux-foundation.org,
        linux-kernel@vger.kernel.org, Julian Anastasov <ja@ssi.bg>,
        Len Brown <len.brown@intel.com>
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On Fri, Mar 30, 2012 at 6:13 AM, Len Brown <lenb@kernel.org> wrote:
> From: Julian Anastasov <ja@ssi.bg>
>
>        commit 64b3db22c04586997ab4be46dd5a5b99f8a2d390 (2.6.39),
> "Remove use of unreliable FADT revision field" causes 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
>
>        The fix is to update acpi_gbl_FADT.header.length after
> the original value is used to check for old revisions.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=42700
> https://bugzilla.redhat.com/show_bug.cgi?id=727865
>
> Signed-off-by: Julian Anastasov <ja@ssi.bg>
> Acked-by: Bob Moore <robert.moore@intel.com>
> Signed-off-by: Len Brown <len.brown@intel.com>

This one should go into the stable trees.  The bug it fixes causes a
number of machines to not boot with anything newer than 2.6.38.

josh