Re: [Xen-devel] x86-64 tools fix question

[Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>]

On 1 Mar 2005, at 19:56, Jerone Young wrote:

>         I'm assuming this has a convenient side-effect that it prevents read
> reordering. Otherwise I can't figure out why this is being done at all.
> Now I'm guessing that that using rsp instead of esp since we are in
> 64bit mode will give the same effect needed.
>
> #elif defined(__x86_64__)
> #define rmb() __asm__ __volatile__ ( "lock; addl $0,0(%%rsp)" : : :
> "memory" )
> #define wmb() __asm__ __volatile__ ( "" : : : "memory" )
>
>
>         I would like to discuss is this correct, dead wrong, or even needed at
> all?
x86/64 has proper barrier instructions -- see 
include/asm-x86_64/system.h in Linux. It is from there that we should 
pull our definitions. Barrier macros are defined in a few places in the 
tools -- we ought to pull them all into one single header incorporated 
by all tools that need it.
 -- Keir



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