Messages in this thread | | | Date | Fri, 2 May 2014 22:30:44 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [RFC/HACK] x86: Fast return to kernel |
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On Fri, 2 May 2014, Linus Torvalds wrote:
> On Fri, May 2, 2014 at 12:31 PM, Linus Torvalds > <torvalds@linux-foundation.org> wrote: > > > > Also, are you *really* sure that "popf" has the same one-instruction > > interrupt shadow that "sti" has? Because I'm not at all sure that is > > true, and it's not documented as far as I can tell. In contrast, the > > one-instruction shadow after "sti" very much _is_ documented. > > Yeah, I'm pretty sure about this. The only instructions with an > interrupt shadow are "sti", "mov ss" and "pop ss". > > There may be specific microarchitectures that do it for a "popf" that > enables interrupts too, but that is not documented _anywhere_ I could > find.
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 ?
Thanks,
tglx
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