[Hardy] SRU: Fix boot panic on Acer Aspire One

[Stefan Bader]

Tim Gardner wrote:
> Stefan Bader wrote:
>> SRU Justification:
>>
>> Impact: Certain kernel versions cause a kernel panic on the Acer Aspire
>> One when the kernel changes its data to read-only pages. The underlying
>> problem is very timing sensitive (adding printks for debugging makes the
>> problem much less likely to occur).
>>
>> Fix: As far as we understand, there might be another thread being
>> running (with a very speculative maybe related to freeing init memory)
>> which gets badly confused by the global_flush_tlb() (could also be
>> affected by the fact that changing the page attributes splits a large
>> kernel page). To prevent that we force all other CPUs to run the stop
>> work function, which basically acts like a  big sync. The performance
>> impact is minimal as this is done only once on boot.
>>
>> Testcase: Booting testkernel on the Acer Aspire One and for comparison
>> on a Dell Inspiron 1521. The Acer succeeds in rebooting without panic
>> and the Dell still does the same.
>>
>> -- 
>>
>> When all other means of communication fail, try words!
>>
>>
> 
> NACK - Shouldn't this be quirked for the Acer platform? I think this
> looks like a total hack and has global i386 impact.
> 
It probably can be. Though we thought it should be without any impact for 
others as all that is done is forcing all CPUs to execute a completely void 
function and by that force them to flush/update their context.
But I go and add some quirking around it.

Stefan

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