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From: Ingo Molnar <mingo@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Borislav Petkov <bp@suse.de>, Rik van Riel <riel@surriel.com>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	x86-ml <x86@kernel.org>, lkml <linux-kernel@vger.kernel.org>
Subject: Re: [GIT PULL] x86 FPU changes for 5.2
Date: Tue, 7 May 2019 22:12:28 +0200	[thread overview]
Message-ID: <20190507201228.GA64489@gmail.com> (raw)
In-Reply-To: <CAHk-=wh4Cjb1qDj_VRW9W4d4n9WLksgMKF-roG8eCk_O0ZaEEg@mail.gmail.com>


* Linus Torvalds <torvalds@linux-foundation.org> wrote:

> On Tue, May 7, 2019 at 6:26 AM Borislav Petkov <bp@suse.de> wrote:
> >
> > This branch contains work started by Rik van Riel and brought to 
> > fruition by Sebastian Andrzej Siewior with the main goal to optimize 
> > when to load FPU registers: only when returning to userspace and not 
> > on every context switch (while the task remains in the kernel).
> 
> 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. 
> 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)?
> 
> I've pulled it, but I'd still like to feel safer about it 
> after-the-fact ;)

Most of the x86/fpu commits except the final one are several weeks old, 
but I have to admit that our old-systems testing is hit and miss, and FPU 
bugs do tend to have an additional 'bug report latency' multipier of a 
factor of 3 or so ...

I've been running all this (modulo the final commit) on my primary 
desktop and other systems as well, FWIIW.

Thanks,

	Ingo

  parent reply	other threads:[~2019-05-07 20:12 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-05-07 13:26 Borislav Petkov
2019-05-07 17:35 ` Linus Torvalds
2019-05-07 17:59   ` Borislav Petkov
2019-05-07 20:12   ` Ingo Molnar [this message]
2019-05-07 21:59   ` Sebastian Andrzej Siewior
2019-05-07 17:55 ` pr-tracker-bot

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