Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC

From: Ingo Molnar (mingo_at_elte.hu)
Date: 04/07/05

  • Next message: Oliver Neukum: "Re: non-free firmware in kernel modules, aggregation and unclear copyright notice." 
    Date:	Thu, 7 Apr 2005 16:51:50 +0200
To: Linus Torvalds <torvalds@osdl.org>

    * Linus Torvalds <torvalds@osdl.org> wrote:

    > > > pushfl

    > After all, I very strongly suspect that we don't actually really
    > _care_ if eflags stays the same over a system call, and I could see
    > that some dynamic CPU's might prefer not having to push an eflags
    > value that just got changed by the "sti", so it _might_ save several
    > cycles to avoid that dependency, and also obviously avoid a subtle
    > dependency on a sw level that the previous patch clearly introduced.
    >
    > Anybody willing to time it? ;)

    i can tell you without any measurement that pushfl is slower by a couple
    of cycles than a simple pushl $0x00010046, on basically all x86 CPUs.
    And since we only support SYENTER from 32-bit mode and we dont guarantee
    flags to be saved, it isnt all that incorrect to do?

            Ingo
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  • Next message: Oliver Neukum: "Re: non-free firmware in kernel modules, aggregation and unclear copyright notice."

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