Re: [Xen-devel] [PATCH v1 02/10] iommu: Add extra order argument to the IOMMU APIs and platform callbacks

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 16.05.17 at 14:48, <olekstysh@xxxxxxxxx> wrote:
> On Mon, May 15, 2017 at 3:33 PM, Jan Beulich <JBeulich@xxxxxxxx> wrote:
>>>>> On 15.05.17 at 12:43, <olekstysh@xxxxxxxxx> wrote:
>>> Indeed, there was some misunderstanding from my side on this.
>>> Let me elaborate a bit more on this:
>>> 1. Yes, this TODO shouldn't be just dropped, but needs to be
>>> addressed, so at least I will have them back in the patch
>>> 2. I am not a x86 guy and not familiar with the Intel/AMD IOMMUs, so
>>> it makes me lots of work to do this change
>>> properly, so this is not only the question of testing the code, but rather
>>> having it written.
>>> 3. Please correct me if I'm wrong, but these are all *optimizations* which
>>> I am mentioning in that TODO, not something that breaks x86 or affects it
>>> in any way.
>>>
>>> That being said, can we postpone implementation of the *optimizations*
>>> in question
>>> and have those as a separate activity?
>>> Or if these *optimizations* must be present in the current patch
>>> series, could you, please, provide me with some hints how
>>> these TODO should be properly implemented?
>>
>> I'm puzzled. When I first commented on these TODOs I did say
>> "While I appreciate this not being done in the already large patch,
>> I don't think such a TODO should be left around. If need be (e.g.
>> because you can't test the change), get in touch with the
>> maintainer(s)." Of course the "e.g." extends to the actual
>> implementation. IOW I'm not saying you need to do this work
>> immediately and all by yourself, but there should be a clear plan
>> on getting these items addressed. We shouldn't ship several
>> releases with them still present. I'm sorry this hits you, but we've
>> had too bad experience in the past with people leaving todo or
>> fixme notes in the code, perhaps even promising to address them
>> without ever doing so.
> I see. You are right about leaving TODO)
> Don't mind to get these items addressed *within current patch series*
> as separate patch or patches.
> So, we have to address for three IOMMUs: Intel/AMD and SMMU. I will
> leave SMMU for myself.
> 
> Could you, please, provide me with some hints how these TODO should be
> properly implemented?

I have to admit that I don't really understand the request. Quite
clearly we want to use large pages in the case that hardware
supports them.

> I was thinking I can even just squash *pages with *page and send you a
> draft as we need to start from somewhere.

I'm afraid I've lost too much of the context to see what you mean
here.

Jan


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