linux-kernel - Re: [RFT v2] iommu/amd: use subsys

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Date:	Mon, 18 Apr 2016 10:02:24 +0300
From:	Oded Gabbay <oded.gabbay@...il.com>
To:	"Luis R. Rodriguez" <mcgrof@...nel.org>
Cc:	Christian König <christian.koenig@....com>,
	"Linux-Kernel@...r. Kernel. Org" <linux-kernel@...r.kernel.org>,
	iommu@...ts.linux-foundation.org, Joerg Roedel <joro@...tes.org>
Subject: Re: [RFT v2] iommu/amd: use subsys_initcall() on amdv2 iommu

On Mon, Apr 18, 2016 at 9:55 AM, Luis R. Rodriguez <mcgrof@...nel.org> wrote:
>
> On Apr 18, 2016 7:48 AM, "Oded Gabbay" <oded.gabbay@...il.com> wrote:
>>
>> On Wed, Apr 13, 2016 at 1:07 AM, Luis R. Rodriguez <mcgrof@...nel.org>
>> wrote:
>> > On Mon, Apr 11, 2016 at 03:52:43PM +0200, Christian König wrote:
>> >> Am 11.04.2016 um 15:39 schrieb Oded Gabbay:
>> >> >On Mon, Apr 11, 2016 at 4:28 PM, Christian König
>> >> ><christian.koenig@....com> wrote:
>> >> >>Am 09.04.2016 um 02:25 schrieb Luis R. Rodriguez:
>> >> >>>On Tue, Mar 29, 2016 at 10:41 AM, Luis R. Rodriguez
>> >> >>> <mcgrof@...nel.org> wrote:
>> >> >>>>We need to ensure amd iommu v2 initializes before
>> >> >>>>driver uses such as drivers/gpu/drm/amd/amdkfd/kfd_module.c,
>> >> >>>>to do this make its init routine a subsys_initcall() which
>> >> >>>>ensures its load init is called first than modules when
>> >> >>>>built-in.
>> >> >>>>
>> >> >>>>This reverts the old work around implemented through commit
>> >> >>>>1bacc894c227fad8a7 ("drivers: Move iommu/ before gpu/ in
>> >> >>>> Makefile"),
>> >> >>>>instead of making the dependency implicit by linker order this
>> >> >>>>makes the ordering requirement explicit through proper kernel
>> >> >>>>APIs.
>> >> >>>>
>> >> >>>>Cc: Oded Gabbay <oded.gabbay@....com>
>> >> >>>>Cc: Christian König <christian.koenig@....com>
>> >> >>>>Signed-off-by: Luis R. Rodriguez <mcgrof@...nel.org>
>> >> >>
>> >> >>Sorry for not responding earlier. Just coming back to all the stuff
>> >> >> on my TODO list.
>> >> >>
>> >> >>Patch is Acked-by: Christian König <christian.koenig@....com>
>> >> >
>> >> >Christian,
>> >> >Just wanted to be sure if you tested this patch-set or not.
>> >>
>> >> I did NOT tested it. If AMD IOMMU requires something which will now
>> >> initialize after the IOMMU module we will obviously run into trouble
>> >> again.
>> >>
>> >> I assumed that the creator of the patch did some testing.
>> >
>> > Nope, hence [RTF] Request For Testing.
>> >
>> >> >I don't think it should be merged without testing. If you already
>> >> >tested it than fine. If not, I think I can do it in the next week or
>> >> >so (just came back from PTO).
>> >>
>> >> Yeah, agree totally.
>> >
>> > Agreed, please let me know if someone is able to test and confirm
>> > this works. It should work.
>> >
>> >   Luis
>>
>> Hi,
>> So I finally got to test this patch and it's not working.
>> The reason is that AMD IOMMUv2 gets initialized *before* AMD IOMMUv1
>> driver !
>
> Thanks can you try using late_initcall() instead then?
>
>   Luis

That will make it initialize *after* drm subsystem, which will cause
another bug.

Oded