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

* Linus Torvalds <[email protected]> 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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---

• References:
  • crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Ingo Molnar <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Stas Sergeev <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Linus Torvalds <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Stas Sergeev <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Linus Torvalds <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Stas Sergeev <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Ingo Molnar <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Andrew Morton <[email protected]>
  • Re: crash in entry.S restore_all, 2.6.12-rc2, x86, PAGEALLOC
    • From: Linus Torvalds <[email protected]>

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