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Re: [Qemu-devel] [PATCH RFC v3 11/14] intel_iommu: provide its own repla

From: Peter Xu
Subject: Re: [Qemu-devel] [PATCH RFC v3 11/14] intel_iommu: provide its own replay() callback
Date: Mon, 16 Jan 2017 16:06:47 +0800
User-agent: Mutt/1.5.24 (2015-08-30)

On Mon, Jan 16, 2017 at 04:03:22PM +0800, Jason Wang wrote:


> >>>Though I haven't tested with huge pages yet, but this patch should
> >>>both solve above issue? I don't know whether you went over the page
> >>>walk logic - it should both support huge page, and it will skip
> >>>unmapped iova range (at least that's my goal to have this patch). In
> >>>that case, looks like this patch is solving the same problem? :)
> >>>(though without introducing iova_iterate() interface)
> >>>
> >>>Please correct me if I misunderstood it.
> >>Kind of :) I'm fine with this patch, but just want:
> >>
> >>- reuse most of the codes in the patch
> >>- current memory_region_iommu_replay() logic
> >>
> >>So what I'm suggesting is a just slight change of API which can let caller
> >>decide it need to do with each range of iova. So it could be reused for
> >>other things except for replaying.
> >>
> >>But if you like to keep this patch as is, I don't object it.
> >I see. Then I can understand your mean here. I had the same thought
> >before, that's why I exposed the vtd_page_walk with a hook. If you
> >check the page_walk function comment:
> >
> >/**
> >  * vtd_page_walk - walk specific IOVA range, and call the hook
> >  *
> >  * @ce: context entry to walk upon
> >  * @start: IOVA address to start the walk
> >  * @end: IOVA range end address (start <= addr < end)
> >  * @hook_fn: the hook that to be called for each detected area
> >  * @private: private data for the hook function
> >  */
> >
> >So I didn't implement the notification in page_walk at all - but in
> >the hook_fn. If any caller that is interested in doing something else
> >rather than the notification, we can just simply export the page walk
> >interface and provide his/her own "hook_fn", then it'll be triggered
> >for each valid page (no matter a huge/small one).
> >
> >If we can have a more general interface in the future - no matter
> >whether we call it iova_iterate() or something else (I'll prefer the
> >hooker way to do it, so maybe a common page walker with a hook
> >function), we can do it simply (at least for Intel platform) based on
> >this vtd_page_walk thing.
> >
> >Thanks,
> >
> >-- peterx
> Yes but the problem is hook_fn is only visible inside intel iommu code.


Btw, do we have existing issue that can leverage this interface
besides replay?

-- peterx

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