Messages in this thread | | | Date | Thu, 15 Jun 2017 17:33:22 +0200 | From | Borislav Petkov <> | Subject | Re: [PATCH v6 26/34] iommu/amd: Allow the AMD IOMMU to work with memory encryption |
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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.
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