linux-kernel - Re: [all better] Re: regression: massive trouble with fpu rework

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Message-ID: <1435505954.5439.22.camel@gmail.com>
Date:	Sun, 28 Jun 2015 17:39:14 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Henrique de Moraes Holschuh <hmh@....eng.br>
Cc:	Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [all better] Re: regression: massive trouble with fpu rework

On Sun, 2015-06-28 at 12:06 -0300, Henrique de Moraes Holschuh wrote:
> On Sun, 28 Jun 2015, Mike Galbraith wrote:
> > > > > > BIOS setting "Limit CPUID Maximum" upsets new fpu code mightily.
> > > 
> > > Well, it is supposed to disable CPUID levels >= 0x04.  This thing should
> > > *NEVER* be enabled, the last operating system that required it to be enabled
> > > was Windows 98.
> > > 
> > > Can/do we override that crap during cpu init?  If we cannot/don't, maybe
> > > instead of limping along with CPUID crippled, it would be better to either
> > > output a very nasty warning, or outright stop booting [with an appropriate
> > > error message] ?
> > 
> > Why get all upset?  We didn't even notice before, nor did/does that
> > other OS.  A casual "BTW, your BIOS sucks.." should suffice, no?
> 
> Oh, I am not upset, although I suppose my reply did look like it.  Sorry
> about that.

I didn't mean you personally of course, I meant the kernel ;-)

> It is just that this kind of breakage should not be subtle if we can help
> it, because people will use a crippled system for years without noticing...

If you can use it without noticing for years, it ain't crippled, or?  My
point being that severity seems more akin to the box having a zit behind
its left ear, in which case lobotomizing it seems a tad extreme.

	-Mike

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