Messages in this thread | | | Date | Wed, 05 Oct 2011 17:17:09 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [PATCH RFC V2 3/5] jump_label: if a key has already been initialized, don't nop it out |
| |
On 10/05/2011 05:16 PM, Jeremy Fitzhardinge wrote: > On 10/04/2011 09:30 AM, H. Peter Anvin wrote: >> On 10/04/2011 07:10 AM, Jason Baron wrote: >>> 1) The jmp +0, is a 'safe' no-op that I know is going to initially >>> boot for all x86. I'm not sure if there is a 5-byte nop that works on >>> all x86 variants - but by using jmp +0, we make it much easier to debug >>> cases where we may be using broken no-ops. >>> >> There are *plenty*. jmp+0 is about as pessimal as you can get. > > As an aside, do you know if a 2-byte unconditional jmp is any more > efficient than 5-byte, aside from just being a smaller instruction and > taking less icache? >
I don't know for sure, no. I probably depends on the CPU.
-hpa
-- H. Peter Anvin, Intel Open Source Technology Center I work for Intel. I don't speak on their behalf.
| |