Messages in this thread | | | Date | Mon, 15 Aug 2022 13:28:11 +0200 | Subject | Re: [PATCH v1] drm/ttm: Refcount allocated tail pages | From | Christian König <> |
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Am 15.08.22 um 13:19 schrieb Dmitry Osipenko: > [SNIP] >>>> I'll try to dig out the older discussions, thank you for the quick >>>> reply! >>> Are you sure it was really discussed in public previously? All I can >>> find is yours two answers to a similar patches where you're saying that >>> this it's a wrong solution without in-depth explanation and further >>> discussions. >> Yeah, that's my problem as well I can't find that of hand. >> >> But yes it certainly was discussed in public. > If it was only CC'd to dri-devel, then could be that emails didn't pass > the spam moderation :/
That might be possible.
>>> Maybe it was discussed privately? In this case I will be happy to get >>> more info from you about the root of the problem so I could start to >>> look at how to fix it properly. It's not apparent where the problem is >>> to a TTM newbie like me. >>> >> Well this is completely unfixable. See the whole purpose of TTM is to >> allow tracing where what is mapped of a buffer object. >> >> If you circumvent that and increase the page reference yourself than >> that whole functionality can't work correctly any more. > Are you suggesting that the problem is that TTM doesn't see the KVM page > faults/mappings?
Yes, and no. It's one of the issues, but there is more behind that (e.g. what happens when TTM switches from pages to local memory for backing a BO).
Another question is why is KVM accessing the page structure in the first place? The VMA is mapped with VM_PFNMAP and VM_IO, KVM should never ever touch any of those pages.
Regards, Christian.
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