Messages in this thread | | | Date | Fri, 2 May 2014 14:01:24 -0700 | Subject | Re: [RFC/HACK] x86: Fast return to kernel | From | Linus Torvalds <> |
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On Fri, May 2, 2014 at 1:30 PM, Thomas Gleixner <tglx@linutronix.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.
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.
Btw, Andy, why did you do "popq %rsp"? That just looks crazy. If the stack isn't contiguous, the subsequent "popf" couldn't have worked anyway. And I bet it screws with the stack engine. So you should just have done something like "addq $16,%rsp" or whatever the constant ends up being.
Linus
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