Re: [patch 8/9] F00F bug fixup for i386 - use conditional calls

Mathieu Desnoyers
2007-05-31T21:38:37Z

* Andrew Morton (akpm@linux-foundation.org) wrote:
> On Thu, 31 May 2007 17:07:55 -0400
> Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > * Andrew Morton (akpm@linux-foundation.org) wrote:
> >
> > > > Use the faster conditional calls for F00F bug handling in do_page_fault.
> > > >
> > >
> > > I guess this means that CONDCALL will be enabled on pretty much all i386,
> > > in which case making the whole feature Kconfigurable is starting to look
> > > marginal.
> > >
> > > Perhaps a better approach would have to made this change dependent upon
> > > CONDCALL, rather than forcing it on.
> > >
> >
> > Do you mean making X86_F00F_BUG depend on COND_CALL instead of selecting
> > it ?
>
> yup
>
> > > > + if (cond_call(fix_f00f, do_f00f_workaround(regs, address)))
> > > > + return;
> > >
> > > We do a cond_call() to an inlined function? That's a bit weird, isn't it?
> > >
> >
> > Yes, but it works :) I will add this information to the documentation.
>
> But why does it work? Did the compiler generate an out-of-line copy
> of the function? If so, we'll end up with multiple copies of the function if
> there are other callers. If not, the `inline' was pointless.

Yes, it's doing an out-of-line copy. Just like the compiler would have
done if we place a call to an inline function within a if() { } block.