Messages in this thread | | | Date | Wed, 19 May 2021 10:28:42 -0300 | From | Jason Gunthorpe <> | Subject | Re: [PATCH v8 5/8] mm: Device exclusive memory access |
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On Tue, May 18, 2021 at 07:45:05PM -0400, Peter Xu wrote: > On Tue, May 18, 2021 at 08:03:27PM -0300, Jason Gunthorpe wrote: > > Logically during fork all these device exclusive pages should be > > reverted back to their CPU pages, write protected and the CPU page PTE > > copied to the fork. > > > > We should not copy the device exclusive page PTE to the fork. I think > > I pointed to this on an earlier rev.. > > Agreed. Though please see the question I posted in the other thread: now I am > not very sure whether we'll be able to mark a page as device exclusive if that > page has mapcount>1.
IMHO it is similar to write protect done by filesystems on shared mappings - all VMAs with a copy of the CPU page have to get switched to the device exclusive PTE. This is why the rmap stuff is involved in the migration helpers
Jason
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