On Mon, Mar 10, 2014 at 2:20 PM, Linus Torvalds <torva...@linux-foundation.org> wrote: > On Mon, Mar 10, 2014 at 1:19 PM, Linus Torvalds > <torva...@linux-foundation.org> wrote: >> >> If the only immediate problem is the code generation size, then Andy >> already had a (simpler) hack-around: >> >> #undef CONFIG_OPTIMIZE_INLINING >> #undef CONFIG_X86_PPRO_FENCE >> >> in vclock_gettime.c > > Btw, we should seriously consider getting rid of CONFIG_X86_PPRO_FENCE. > > It was of questionable value to begin with, and I think that the > actual PPro bug is about one of > > - Errata 66, "Delayed line invalidation". > - Errata 92, "Potential loss of data coherency" > > both of which affect all PPro versions afaik (there is also a UP > errata 51 wrt ordering of cached and uncached accesses that was fixed > in the sB1 stepping). > > And as far as I know, we have never actually seen the bug in real > life, EVEN WHEN PPRO WAS COMMON. The workaround was always based on > knowledge of the errata afaik.
I admit I don't fully follow the description of the errata, but it's not obvious to me that making smp_rmb() emit lfence is going to do any good. The description seems to be suggesting using actual LOCK operations to work around the erratum. > > So I do think we might want to consider retiring that config option > entirely as a "historical oddity". > > And very much so for the vdso case. Do we even do the asm alternative > fixups for the vdso? Yes, we've done that for a couple years for rdtsc_barrier's benefit. > > I also suspect we should get rid of CONFIG_X86_OOSTORE, or at least > limit it to !SMP - I don't think anybody ever made SMP systems with > those IDT/Centaur Winchip chips in them. Why does OOSTORE matter for !SMP? Is it just for poking at hardware registers? --Andy -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/