Re: [GIT PULL] x86 FPU changes for 5.2

From: Borislav Petkov
Date: Tue May 07 2019 - 14:00:15 EST

On Tue, May 07, 2019 at 10:35:25AM -0700, Linus Torvalds wrote:
> I love this and we should have done it long ago, but I also worry that
> every time we've messed with the FP state, we've had interesting bugs.

Tell me about it. Our FPU code is one helluva contraption.

> Which is obviously why we didn't do this long ago.
> Has this gone through lots of testing, particularly with things like
> FP signal handling and old machines that don't necessarily have
> anything but the most basic FP state (ie Pentium class etc)?

Right, so I ran it on the bunch of boxes I have here, the oldest is a K8
which has:

[ 0.000000] x86/fpu: x87 FPU will use FXSAVE

and it looked ok. Ingo ran it on his fleet too, AFAIR.

Lemme see if I can dig out something older at work.

> I've pulled it, but I'd still like to feel safer about it after-the-fact ;)



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