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SubjectRe: Ingo's PIII FXSTOR patch [2 Mar] causes problems

On 16 Apr 1999, Linus Torvalds wrote:

> I haven't looked into the exact details, but I guess you're referring to
> the fact that fxsave only saves the "empty" bit.
>
> That's not lossy: the rest of the tag information is implicit in the
> actual value of the stack entry.
>
> It shoul dbe really easy to convert between the new and the old format:
> let the hardware do it for you:
>
> fxrestore new-format
> fnsave old-format
>
> I don't see any loss of information anywhere.. Am I overlooking
> something?

yep this should work. (i optimized this because the above takes about 300
cycles to do, but it's an incorrect approach) But i doubt this is the
cause of the numeric instability observed, nothing i know of relies on the
tag/status word exported through the ptrace interface. [but i agree that
we should be rather correct than fast]

Ingo


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