Messages in this thread | | | From | Alistair Popple <> | Subject | Re: [PATCH v7 5/8] mm: Device exclusive memory access | Date | Thu, 1 Apr 2021 00:27:52 +1100 |
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On Thursday, 1 April 2021 12:18:54 AM AEDT Jason Gunthorpe wrote: > On Wed, Mar 31, 2021 at 11:59:28PM +1100, Alistair Popple wrote: > > > I guess that makes sense as the split could go either way at the > > moment but I should add a check to make sure this isn't used with > > pinned pages anyway. > > Is it possible to have a pinned page under one of these things? If I > pin it before you migrate it then it remains pinned but hidden under > the swap entry?
At the moment yes. But I had planned (and this reminded me) to add a check to prevent marking pinned pages for exclusive access. This check was in the original migration based implementation as I don't think it makes much sense to allow exclusive access to pinned pages given it indicates another device is possibly using it.
> So the special logic is needed and the pinned page has to be copied > and written as a normal pte, not dropped as a migration entry
Yep, if we end up allowing pinned pages to exist under these then that makes sense. Thanks for the clarification.
- Alistair
> Jason >
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