Re: [PATCH 1/3] amdkfd: Don't clear *kfd2kgd on kfd_module_init

[Oded Gabbay]

On 12/22/2014 11:26 AM, Oded Gabbay wrote:
> On 12/22/2014 10:57 AM, Christian KÃnig wrote:
> > Am 22.12.2014 um 08:43 schrieb Oded Gabbay:
> > > On 12/22/2014 09:40 AM, Dave Airlie wrote:
> > > > > > > > > There should be, but when the modules are compiled in, they are loaded
> > > > > > > > > based on
> > > > > > > > > link order only, if they are in the same group, and the groups are
> > > > > > > > > loaded by a
> > > > > > > > > pre-defined order.
> > > > > > > >
> > > > > > > > Is that really still up to date? I've seen effort to change that
> > > > > > > > something like
> > > > > > > > 10+ years ago when Rusty reworked the module system. And it is comming
> > > > > > > > up on the
> > > > > > > > lists again from time to time.
> > > > > > >
> > > > > > >  From what I can see in the Makefile rules, code and google, yes, that's
> > > > > > > still
> > > > > > > the situation. If someone will prove me wrong I will be more than happy
> > > > > > > to
> > > > > > > correct my code.
> > > > > > > > > I don't want to move iommu before gpu, so I don't have a solution for
> > > > > > > > > the
> > > > > > > > > order between amdkfd and amd_iommu_v2.
> > > > > > > >
> > > > > > > > Why not? That's still better than creating a kernel workqueue,
> > > > > > > > scheduling one
> > > > > > > > work item on it, rescheduling the task until everything is completed and
> > > > > > > > you can
> > > > > > > > continue.
> > > > > > >
> > > > > > > Because I don't know the consequences of moving an entire subsystem in
> > > > > > > front
> > > > > > > of another one. In addition, even if everyone agrees, I'm pretty sure
> > > > > > > that
> > > > > > > Linus won't be happy to do that in -rc stages. So maybe this is something
> > > > > > > to
> > > > > > > consider for 3.20 merge window, but I would still like to provide a
> > > > > > > solution
> > > > > > > for 3.19.
> > > > > >
> > > > > >
> > > > > > Yeah, true indeed. How about depending on everything being compiled as
> > > > > > module
> > > > > > for 3.19 then? Still better than having such a hack in the driver for as a
> > > > > > temporary workaround for one release.
> > > > > I thought about it, but because this problem was originally reported by a
> > > > > user that told us he couldn't use modules because of his setup, I decided
> > > > > not to.
> > > > > I assume there are other users out there who needs this option (compiled
> > > > > everything in the kernel - embedded ?), so I don't want to make their life
> > > > > harder.
> > > > >
> > > > > In addition, saying it is a workaround for one release is true in case
> > > > > moving iommu subsystem in front of gpu subsystem is acceptable and doesn't
> > > > > cause other problems, unknown at this point.
> > > > >
> > > > > Bottom line, my personal preference is to help the users _now_ and if a
> > > > > better fix is found in the future, change the code accordingly.
> > > >
> > > > My guess is moving the iommu subsystem in front of the GPU would be rational.
> > > >
> > > > It does seem like it would generally have a depend in that order.
> > > >
> > > > Dave.
> > > Dave,
> > > I agree, but don't you think it is too risky for -rc stages ?
> > > If not, I can try it and if it works on KV, I can submit a patch.
> > > But if you do think it is risky, what do you recommend for 3.19 ? Do the fix I
> > > suggested or disable build-in compilation option ?
> >
> > I would say create the patch of changing the order (should be trivial), describe
> > in detail in the commit message what this is supposed to fix and why such an
> > severe change was done in -rc1 and submit it upstream.
> >
> > We can still revert it in -rc2 if it breaks anything.
> >
> > Christian.
> >
> > >     Oded
>
> OK, I'll try it on my machine and if it works, I will send the patch to the list.
>
>      Oded
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So I checked it and all my HSA tests are passing on KV machine.
I will send the patches today. Please discard the current patch-set.

	Oded
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