[Fwd: Re: [PATCH] x86: Relegate CONFIG_PAT to EMBEDDED]

[Tim Gardner]

Daniel J Blueman wrote:
> On Tue, Oct 13, 2009 at 2:10 PM, Tim Gardner <tim.gardner at canonical.com> wrote:
>> Daniel J Blueman wrote:
>>> On Tue, Oct 13, 2009 at 2:18 AM, Tim Gardner <tim.gardner at canonical.com> wrote:
>>>> Tim Gardner wrote:
>>>>> Andy, Stefan - Why _is_ it that we don't have PAT enabled? Wasn't it
>>>>> originally a prerequisite for KMS back in Jaunty days?
>>>>>
>>>>> There are some comments on LKML pointing out that we _should_ have PAT
>>>>> enabled, e.g., "[RFC Patch] use MTRR for write combining if PAT is not
>>>>> available"
>>>>>
>>>>> rtg
>>>>>
>>>> http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-karmic.git;a=commit;h=a611fa50121f1698bd367b991f66e2268eb10824
>>> Excellent. Is the idea that this will be a karmic beta update in a
>>> couple of days, and we have a get-out-of-jail of disabling it (or
>>> default boot with 'nopat') before the final release is cut?
>>>
>>> Or, is this simply too late to make the final release?
>>>
>>> Daniel
>> Kernel freeze is Thursday. With the addition of stable and other
>> miscellaneous patches, today's upload is going to be the last one
>> (unless some OMG kitten killer gets in my face).
> 
> Ok, great.
> 
> Still of importance, so worth mentioning here, CONFIG_X86_MCE gives
> visibility of otherwise silent memory controller and/or internal
> processor state (including processor passing critical temperature
> thresholds).
> 
> This is particularly crucial for servers with lots of memory
> (therefore higher chance of cell failure), but also modern desktops
> having larger amounts of memory. From a support perspective, detected
> memory errors are logged to the kernel log. From a user perspective
> (particularly for ubuntu-server), the user knows more when they have
> eg failing/faulty memory. I'd think twice about deploying critical
> services on a server where (un)correctable ECC errors *silently*
> occur...
> 
> Since this feature has been around really a long time, it carries no
> risk. Thoughts?

Frankly, I've no idea why it _isn't_ enabled. Since Karmic is really the
test release for Lucid, I'm gonna turn it on.

http://kernel.ubuntu.com/git?p=ubuntu/ubuntu-karmic.git;a=commit;h=ecae83a7adca974982267a4084a30033de9b6b22

I'm not too concerned about MCE working correctly on 64 bit platforms,
but I've a bit more concern about older 32 bit CPUs.

rtg
-- 
Tim Gardner tim.gardner at canonical.com