Messages in this thread | | | Date | Fri, 15 Aug 2008 15:44:10 -0700 (PDT) | From | Linus Torvalds <> | Subject | Re: [PATCH] ftrace: use only 5 byte nops for x86 |
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On Fri, 15 Aug 2008, H. Peter Anvin wrote:
> Ingo Molnar wrote: > > > > > > > > TODO: Examine the cpuid to determine the nop to use. > > > > > > > Don't think that will help in general. qemu claims its a Pentium II. > > > > ok. I've applied Steve's patch as it's a good bugfix. The extra paranoia > > about faulting on 0x90 seems excessive but doesnt hurt ;-) > > > > I think what we need to do is to test the NOPL instruction and create a > Linux-specific CPUID bit for it. I'll do that and submit to tip:x86/cpu.
I also suspect that we'd really be much better off just fixing the generic NOP tables for the 5-byte nop. As far as I could tell, from all the numbers that have been posted, absolutely _none_ show that there is any point at all to the 2-instruction 3/2-byte sequence.
So instead of having a magic special ftrace-only thing, why not just do it right, and fix the generic 5-byte nop sequence?
Linus
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