Re: [RFC 00/15] x86_64: Optimize percpu accesses

[H. Peter Anvin]

Jeremy Fitzhardinge wrote:
> No, you do it the same as i386.  You set the segment base to be 
> percpu_area-__per_cpu_start, and then just refer to %gs:per_cpu__foo 
> directly.  You can use rip-relative addressing to make it a smaller 
> addressing mode too:
>
>   0:    65 89 05 00 00 00 00     mov    %eax,%gs:0(%rip)        # 0x7

Thinking about this some more, I don't know if it would make sense to 
put the x86-64 stack canary at the *end* of the percpu area, and 
otherwise use negative offsets.  That would make sure they were readily 
reachable from %rip-based references from within the kernel text area.

	-hpa
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