Rusty Russell wrote:
> There are several issues to answer here. First, that "set_fixaddr_top"
> above would need to be in an #ifdef or otherwise wrapped for the
> non-paravirt case.
>
Well, that's simple and self-contained. Besides, by the time we're done
there won't be a need for !PARAVIRT ;)
> Secondly, *if* the only thing that will actually alter the fixaddr_top
> is paravirt, it makes sense to keep it a constant except in the paravirt
> case, ie:
>
Gerd's original patch also supported a kernel parameter to set it. Was
that for anything in particular?
> #ifdef CONFIG_PARAVIRT
> #define __FIXADDR_TOP (paravirt_ops.linear_top)
> #else
> #define __FIXADDR_TOP 0xfffff000
> #endif
>
> This is simpler and clearer than indirecting through another function
> (set_fixaddr_top) and another variable (__FIXADDR_TOP).
>
If code assumes it is a simple compile-time constant in the non-paravirt
case, it will break paravirt. At least making it clearly C syntax will
prevent people from putting it into asm or .lds files.
But it still seems to me it could be a variable either way. Are there
any performance-critical users of it?
J
