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

Andrew Morton
2007-05-31T21:22:00Z

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.