linux-kernel - Re: [RFC/HACK] x86: Fast return to kernel

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Message-ID: <alpine.DEB.2.02.1405022327460.6261@ionos.tec.linutronix.de>
Date:	Fri, 2 May 2014 23:28:39 +0200 (CEST)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
cc:	Andy Lutomirski <luto@...capital.net>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	the arch/x86 maintainers <x86@...nel.org>,
	"H. Peter Anvin" <h.peter.anvin@...el.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Gleb Natapov <gleb@...nel.org>,
	Paolo Bonzini <pbonzini@...hat.com>
Subject: Re: [RFC/HACK] x86: Fast return to kernel

On Fri, 2 May 2014, Linus Torvalds wrote:

> On Fri, May 2, 2014 at 1:30 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> >
> > So what about manipulating the stack so that the popf does not enable
> > interrupts and do an explicit sti to get the benefit of the
> > one-instruction shadow ?
> 
> That's what I already suggested in the original "I don't think popf
> works" email.

Missed that.
 
> It does get more complex since you now have to test things (there are
> very much cases where we get page faults and other exceptions with
> interrupts disabled), but it shouldn't be much worse.

Right. The extra conditional is probably not noticable at all.

Thanks,

	tglx
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