Messages in this thread | | | Date | Wed, 21 Jul 1999 08:24:52 +0100 | From | BOSZORMENYI Zoltan <> | Subject | Re: Linux 2.2.11pre2 proposed patch |
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Steve Dodd wrote: > > On Tue, Jul 20, 1999 at 12:41:40PM +0100, BOSZORMENYI Zoltan wrote: > > > Well, then will you please remove the f00f bugfix as well > > and develop a user space tool to switch it on? > > (The sarcastic taste was intended. :-)) > > IMHO the processor bug workarounds should be in the > > the kernel. > > I personally feel that all the (reasonably small) CPU workarounds should be > in the kernel, but I seem to have lost that battle. The idea that all the
Maybe Alan Cox can be convinced this time with _proper_ information. (At least it seemed so in his mail.)
> distributions are going to include start-up scripts which grep /proc/cpuinfo > and run set6x86 accordingly is ludicrous wishful thinking IMHO.
Well, I think that the proper approach is that everything that controls processor behaviour belongs to the kernel. Just an example: someone complained to me that he set ARRs with set6x86 and /proc/mtrr did not reflect the changes...
> To address your first point, I think the f00f bugfix has to be kernel space. > It seems to mess with mm things (does this indicate how little I understand > about it? :)
It changes the interrupt descriptor table layout, as far as I understand it. And I said it only for fairness. :-)
> > And if the bugfix itself causes the file corruption then > > no matter where you enable the bugfix and which tool you use... > > Note that there are two different techniques for working around the bug: > > - set the NO_LOCK bit in CR<whatever>; can cause problems in obscure > circumstances (Alan mentioned a graphics / accelerator card problem)
To repeat myself: this crept into linux-2.2.8, ...
> - do some undocumented magic provided by (or reverse engineered from) > Cyrix, that seems to modify the CPU behaviour when executing the > offending instruction, making to do a noop afterwards. I don't know > of any problems caused by this.
... and this is already in 2.2.10. Don't you guys read the code others write? :-(
Best regards, Zoltan Boszormenyi
-- Microsoft: It's where you don't want to go today.
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