On Thu, Jun 15, 2017 at 09:59:45AM -0500, Tom Lendacky wrote: > Actually the detection routine, amd_iommu_detect(), is part of the > IOMMU_INIT_FINISH macro support which is called early through mm_init() > from start_kernel() and that routine is called before init_amd(). Ah, we do that there too: for (p = __iommu_table; p < __iommu_table_end; p++) { Can't say that that code with the special section and whatnot is obvious. :-\ Oh, well, early_init_amd() then. That is called in start_kernel->setup_arch->early_cpu_init and thus before mm_init(). > > If so, it did work fine until now, without the volatile. Why is it > > needed now, all of a sudden? > > If you run checkpatch against the whole amd_iommu.c file you'll see that I'm, of course, not talking about the signature change: I'm *actually* questioning the need to make this argument volatile, all of a sudden. If there's a need, please explain why. It worked fine until now. If it didn't, we would've seen it. If it is a bug, then it needs a proper explanation, a *separate* patch and so on. But not like now, a drive-by change in an IOMMU enablement patch. If it is wrong, then wait_on_sem() needs to be fixed too. AFAICT, wait_on_sem() gets called in both cases with interrupts disabled, while holding a lock so I'd like to pls know why, even in that case, does this variable need to be volatile. -- Regards/Gruss, Boris. Good mailing practices for 400: avoid top-posting and trim the reply. -- To unsubscribe from this list: send the line "unsubscribe linux-doc" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html