* Andrew Morton ([EMAIL PROTECTED]) wrote: > On Fri, 1 Jun 2007 02:14:53 +0200 (MEST) > Mikael Pettersson <[EMAIL PROTECTED]> wrote: > > > Andrew Morton wrote: > > > Mathieu Desnoyers <[EMAIL PROTECTED]> wrote: > > > > > > > * Andrew Morton ([EMAIL PROTECTED]) 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 > > > > X86_F00F_BUG needs to be enabled in all kernels capable of booting on > > P5 class machines, whether or not some obscure CONFIG_COND_CALL thingy > > is enabled or not. X86_F00F_BUG is not some optional optimisation, it's > > an essential workaround for a serious hardware bug. > > > > Therefore it seems select rather than depend is called for. > > Nope. > > CONFIG_COND_CALL=n -> do f00f handling the present way > CONFIG_COND_CALL=y -> do f00f handling the new, fast-n-fancy way > > > Because I don't think everyone will want to drag all this cond_call stuff > into their kernel just for slightly faster f00f handling. >
Then I should probably leave the redundant if (boot_cpu_data.f00f_bug) test in do_f00f_workaround so that configuration where cond_calls are not enabled still behave the same way as before. The redundant test will make the case when cond calls are present a little slower, but we still have the improvement when the architecture does not need the workaround. I could also wrap this test in a #ifndef CONFIG_COND_CALL, but it seems ugly. Also, since the default is not to set the CF_STATIC_ENABLE flag, the workaround won't be compiled in the kernel if the conditional calls are configured out. The question that arises is : what should be the default behavior of a cond_call when the cond_calls are configured out? Active, active only if the CF_STATIC_ENABLE flags is set or inactive? -- Mathieu Desnoyers Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68 - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
